It gives off serious heat, but should easily run the whole day. This thing is dead simple, but well built. Other than tubes, I don't know what could go out on it.
I was really curious to see how vibration isolation might effect the Miniwatt, but I couldn't easily find anything that worked with such a small component. In the end I tried Herbie vibration rings on all 3 tubes, but didn't notice any changes.
Have you played with isolation at all? Maybe you're more sensible than me and you're just enjoying your music.
I had the same issue with reissue Chinese Gold Lion EL84s dying quickly on the Luxman. They sounded great (briefly) and then I was $200 poorer.
I bought the Create Audio tube upgrade from ALO Audio for the Miniwatt. They seem to be durable and an improvement over the stock tubes.
I also used a power cord and interconnects on the Miniwatt that exceeded the cost of the amplifier by a factor of two. This seems counterintuitive, but I think the Miniwatt merits that sort of consideration.
I bought a Miniwatt to fill in for my Luxman tube amp while it was being repaired. What a surprise it turned out to be. It lacks the remote, multiple inputs and headphone jack of my Luxman, but was a real sonic contender against a piece of gear that cost eight times the price.