I'm with ya Byk 100% now. I've tried LifePo's but after a few years they expanded AND leaked in my precious, you better believe that the light was cleaned and recovered. However, that incident alone scared me away from them (they were cheap Tenergy's I believe).
Nowadays primary's are so cheap it's just common sense to use them in a light like the A2. Not only are they awesome lights, they're long discontinued...
I will say that I tried a cheaper brand of 123's on Amazon (I think they were labeled RavPower or something and had good reviews overall), well they got stuck again my my A2.
Since then I just went to the 'Good Deals' section on CPF itself and stocked up on that sick LAPG deal, I'm set for a long time given that they're guaranteed 10 year shelf life and PROVEN to go WELL beyond that with little to no capacity loss... And they fit. And they won't leak.
A light such as the A2 deserves to be fed with quality primary cells is what I have concluded after owning well over a dozen and having many modified parts for them (one light I've never sold since acquisition is the A2 FYI

). Small price to pay for a guarantee of no worries, I'll mess with my other lights.
ETA: I know I may have sounded to contradict my prior posts, however all I was saying is that I've come full-circle and through all of my prior experiences concluded that quality primary's are the way to go. I guess the only exception would be if you're a heavy A2 user (are many left??) then you may want to consider LifePo's.
I've tried it all, luckily never fried anything!