Mix same drive with different firmware in RAID?

[AMD_Gamer]

If you have the same version of a drive but one is about a year older and has an older firmware is it ok to mix them in RAID? I have the same exact drive but one is from 2009 and has the older firmware and I also have a newer one from July 2010 that has the newer firmware? Would this cause any stability problems?

 

[drescherjm]

I have never had a single problem with this in 10+ years of raid at work (10 to 20 raid arrays > 100 drives total). However most of this was linux software raid.