Is it proper to leave amp on all the time?

Hi, I recently started to try to build a system that for years that I thought was way out of of my league. Going back 35 years ago it just seemed when everybody was so interested in speakers that could blow you off the planet, I walked into a audiophile high fi store & my outlook on stereo forever changed. (Source Linn LP12 turntable to Speakers), better to have a solid front end, working through mid section (Amp, Pre-Amp)and finally speakers. Sub-Par Speakers sound better than good speakers without good source. Anyway enough of that, this is a little bit of an introduction to myself!!! I recently bought a used Rotel DVR 995 $50.00, a used pair Vandersteens 2Cs $450.00,& A brand new NAD 326BEE Integrated Amplifier $450.00 After all of that, my question is that I was told by my Audio Dealer to just leave my amp on all the time, and if that is true, why? Seems like it would shorten lifespan of unit. Also I forgot to mention that along with the Rotel & the Vandersteens, I got Silver Sonic Q10 High Resolution Speaker Cables, Tributaries Audio OFHC Copper Cable Interconnects from the same person that I bought the Rotel & Vandersteens. I like all kinds of music for the most part!!! My dealer said he would give a 100% back on NAD if I was to return it within 2-3 months to upgrade. I was thinking that I would trade for the NAD375BEE which would be the most cost effective, before I went & started on the CD player which I could do the same as the NAD326 to buy some time to save for a nicer CD player. Then Cables, Power Supplies, Speakers etc. What is a good plan to get better sound each time I add something? I do like the idea of a warranty & the expertise of the local dealer who comes highly reccommended we'll see!!! Novice looking for guidance!!!
Some S/S amps require significant warm-up time, say on the order of 24 hours. This is probably the reason for the dealer's recommendation. As far as the life of the amp, it will probably increase it owing fewer tunr-on time current surges.
SS - Yes! 24/7
Tubes - No! Give 1/2 hour to warm up & 1 hour to start sounding normal/fantastic (providing they are broken in).
you might think of it like this: You know how a light bulb most frequently burns out -- blows out, really -- when you switch it on, and not when it's just sitting there glowing? That's because switching it on causes a great big surge, stressing the heck out of the thing. Happens each time you hit the switch. Same thing with your amplifier. It doesn't need the stress -- so just leave it on all the time. Except, of course, when there's a thunder storm rolling into town. Then, turn it off -- and unplug it, too. On the scale of stress, a lightning strike is way above flipping the power switch.