I use the cci#41 primers in the white and black box, for my ar reloads they are a little harder to prevent slam fires, I've never had one one but for $1.00 more per 1000 primers its cheap insurance.

I have the lyman 1200 pro tumbler and it works well, its over a year old and has tumbled thousands of rounds of brass with no trouble.

I would say a case trimmer is a necessity, I usually have to trim every 2-3 times I reload the same lot of brass. on my big game and hi-power rifle loads I check them every time on the trimmer.

as far as how many times on the same brass, there is to many variables such as how hot, and what brand of brass you are using, I would estimate 7-12 times.
I'm no pro, and this is just my .02 take it for what its worth.