Audible Illusions preamps have gotten what I consider an undeserved bad rep for tube life over the years.
I bought a Modulus 3 for my son about 12 years ago. OK, I damn near stole it. I found one in a thrift store with a $115 price tag on it. The tubes lit up and I figured at that price I could pay to repair anything that was wrong with it and still be way ahead of the game. Turns out it worked perfectly and has ever since. They just had no idea what they had, and far be it from me to educate them.
With us moving as a family and they my son moving out on his own I would say over the 12 years it has had about 6 or 7 years worth of regular use. and with all that usage I have replaced two tubes in all that time.
The thing you had to keep in mind with the AI Modulus preamps is that the button that is labels as the power switch does not actually shut down the unit, it just puts it in a standby mode. it it left plugged in , even with the power switch in the off position, tube tubes are running 24/7, which of course puts a lot of run time on those tubes, only a small fraction of which is being used to actually play music. So if you think about it, if you were to play your system for 4 hours every single day without fail you would be running the tube 24 hour to produce 4 hours of music or burning them for 5 extra hours for every hour you listen to them. So most people looked at how often they had to change tubes as a function of listening time and said that the tubes in an AI pre lasted 1/6th as long as when in reality the issue was really that they were running the tubes 6 time more than they needed to.
With this in mind the answer is fairly simple. Rather than using the power switch, which left the tubes running I just started pulling the plug we the unit was not in use. (You could also plug the AI into something with a power switch build into it like a power line conditioner.) Doing With the AC input cut off from the AI power supply the tubes shut down when not in use and mine have lasted just as long as other tube preamp.
Performance wise I think is a a very nice preamp. The only thing I don't like about it is the dual mono volume controls. I just find it a bit bothersome to have to adjust 2 controls to change volume and to have to be concerned with upsetting the L/R balance every time I do. It is a minor nuisance, and other than that I think it is a great sound per $ piece, especially for that you can get one on the used market.
Just to give you a point of reference, my main system uses an Audio Research SP-9 preamp which I bought new in 1988 and I am still very happy with. The AI has a slightly different character to it, but I would say they are definitely in the same league as far as overall sound quality goes.