What do you see as the downside of tubes?

I have decided on getting a tube amp and it will be the integrated Mastersound 300B driving a pair of Living Voice Avatars, so at least that decision has been taken.

My main question is what you see as downsides of having a tube amp. As I've decided on getting an integrated tube it's really about what the downsides are I might want to know about beforehand.

The ones I'm aware are the following.

-The tubes need to be replaced and in the case of a 300B this will be somewhat costly.

-Bias is another issue but I'm not sure how big an issue. Do you plug in your meter every so often or just when you roll tubes or replace a dead one? The meter as such isn't gonna be a big issue as I don't think it's that expensive.

-Heat won't be a big issue as we have no kids nor a nosy dog that could get burned. Hope my electricity bill isn't gonna go through the roof, but then again, I can't quite imagine that.

I'd appreciate if you could add whatever your experiences are regarding this question are as I'd like to know more before I buy it.

I agree with the above comments.

1. Some people like the sound of tubes and like (or tolerate) the process of replacement/tinkering/service/expense with them.

2. Some people do not like (or tolerate) that process, even if they the like the sound.

3. Some people could care less or haven't experienced tubes properly.
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Major downside that has not been mentioned:

You will enjoy music so much more. Holographic imaging, silky midrange, liquid and smooth texture, air and bloom around each note, they are all addictive and intoxicating you might 1) lose sleep and listen all night long, 2) beat yourself up for not trying tube much earlier, 3) trip over cables walking in the dark to see the glowing tubes, 4) lose a few friends trying to save them from the dark side (SS).
I think Mlsstl has it exactly right. Whether you consider the extra fuss that tubes require a downside or an excuse to engage with your equipment depends on your perspective. I've found my Cary pre and amp to require minimal maintenance, just the occasional replacement of tubes as they wear out (and by occasional I mean every several years) and checking the bias of the amp.

Heat is an issue, as is the power demand of the amp.

A very big advantage in my mind is that you can make changes in the sound of your system by rolling tubes. All of the other tweaks you can do to improve sound are common to both tubes and SS, but rolling tubes gives you one more way of fine-tuning the sound.