If using new brass it should work just fine. Used brass you probably should anneal first. I wouldn't think that there would be much if any difference in case life. 
A while back this question was asked, but since I don't have a set of 25-20 dies, I use a set of 218 Bee dies. I annealed a case and then run it through the seater die and then the full length die and it came out just fine. Tried the same thing without annealing the used case and it didn't work at all, pretty much crumpled the case. 
YMMV
Sam

You may find that the use of a 25-20 WCF trim die as an intermediate step will cut down on rejects. Also if you don’t already have one get a can of Imperial sizing die wax. Don’t worry about the expense one can will last you a lifetime.
If annealing be careful, these are short cases and brass is an excellent conductor of heat. Put them in water up to the transition to the neck and lightly torch them. If you go to cherry red that’s too much heat. 

40 Rod

I haven't resized any 32-20s to 25-20s because my 25-20 is a 25-20SS.  But,  I have resized a lot of 30-30 brass to 25-35.  Very simple.  I just use the 25-35 FL die and when I get them finished I trim them in a 25-35 trim die.  Should be jusr the same for 25-20 from 32-20.  I also make my 7mm Mausers for the rolling blocks from military 30-06 brass.  Pretty simple, just don't over lube.  I use a file trim die for that too.

George
Salmon, Idaho

starline works good for me. it is available direct from starline, just have to watch and catch it in stock. it is also less expensive than Remington or Winchester.

Gents- when necking down a standard case such as a 32wcf to a smaller version (25wcf) it is important to have and use a Trim Die for the smaller 25wcf, then full length size the resulting new case.  The interior dimensions of the trim die are slightly oversize so you can trim without excess working brass.  This lets the trim die (which is slightly larger than the final sizer serve as an intermediate die to improve your success.
Try it, be careful, enjoy your new cases-
Chuck V

the 218 to 25-20 dont work so well   lots of splits even with anneal    i just formed 50 32-20 down to 25-20 with no problems. these were rem brand once fired without anneal. i would caution on most "down sizing" tho to be aware of the amount of lube on the case. too much lube will hydraulic creases in the case, usually in the neck   

You should be able to fireform a 218 bee in your 25/20 with no problem