My A2 SE was about a year old when I acquired it so both it and the stock valves were already well run in by the time I got my hands on it. The previous owner told me he hadn't changed the valves and they were still performing nicely so that's about all I can offer you in terms of tube longevity as I have no idea how frequently he used it.
I have now had it for a couple of months and have swapped out the 12AT7s for new old stock CV4024s and the 5687WBs for a pair of NOS Mullard E182CCs. I rolled the CV4024 tubes in first and felt initially this robbed a bit of frequency extension from both ends and led to a flattening of the soundstage. This all came back though after a couple of weeks of use (maybe 30 hours or so) but I found the pair of E182CCs made a more profound improvement to the already excellent presentation. I was hearing things on tracks I had never heard before, separation of instruments was better defined and the soundstage increased by a couple of feet in all directions. If it makes sense, it just made everything sound more "real". The only caveat is that with the Mullards, you can't fit the tube shields back on due to the extra height of the valves but that's no problem...I just left them off.
I'm very happy with the current tube compliment but even the stock tubes impressed me enough to decide to keep this over my Rogue 99 Magnum, that and the flexibilty offered by the balanced inputs/outputs.
Now I should at this point declare that I'll never...ever...ever make it as a hifi reviewer because I'd struggle to compose 1000 words of copy that details a specific sonic landscape...well, that and perhaps more pertinently the fact that I still perceive electricity and all it does as sorcery...not a clue as to how any of it works. So with absolutely no credentials I'll try and address your emailed queries in my own inimitable way...
I'm not sure that I'd describe it as "fast", particularly if you are used to solid state preamps. My last Chord preamp gave a much more upfront presentation that on first listening sounded detailed and 'fast'(?) and I thought it was great at the time. It was only when I heard a valve pre for the first time in my system that I realised just how artificial the solid state experience had been. Because with valves the music seems to flow from the speakers rather than being etched into the sound stage, superficially they can sound softer and perhaps slower. However after a while I realised that this wasn't the case at all. In fact leading edges and transients were improved and I can only liken it to (perhaps unsurprisingly) the differences you'll hear in listening to a decent vinyl rig and a similarly priced digital front end. I have to admit that it took some getting used to but I wouldn't go back to a solid state pre. That was the difference I got with the Rogue and the A2 SE has just taken that and considerably improved upon it.
I am not really a bass fiend and my system is in a small room that can misbehave down low so I have to be careful with bass. My NorthCreek Pegasus speakers are closer to the back wall than I would like and so I have the ports stuffed and run a powered sub to better control the bass output so this probably disqualifies me from stating whether it has a great bottom end or not. I personally like it, I find it detailed and tuneful but how much of it is down to the pre in itself I couldn't possibly say.
My experience with tube rolling is admittedly limited but the amp seems to be responsive. If you find you want better defined bass, more treble sparkle or whatever floats your particular boat then you will probably find a combination of valves that will augment this aspect of its delivery and they are relatively inexpensive as valves go. Whether this will be enough for you in absolute terms I can't say but IMO it really is a quality and capable little preamp.
Now I didn't pay $1500 for it as it was second hand, but having lived with it for a couple of months now I certainly would. Something you need to consider though is that the resale value might depress you if you don't like what valves do for you and you find that you want to sell it on. I think it might be worth your while borrowing a valved pre to see if you like what it does in your system because I at least found it a very different experience.
Anyway, I'm keeping mine and don't have any plans to change it for a good while.
I realise that this brand is less well documented than many others but I think that the reviews from people who actually own this product are very favourable...myself included.
There are those who will counsel the avoidance of imported products 'knocked up' by a guy in his shed where servicing (should it exist) will involve a £200 DHL bill and 12 weeks of amplifier deprivation, and in many cases they'd be right. I'd have to say though that in my opinion/experience this isn't one of those products. It doesn't have the solidity or rack presence that you'll get with many high end brands but it mixes it with them where it counts as the sound quality is superb.
Hope this helps.
