No, you don't need to reduce the minimum training thingumy. Yes, it will give dwarves breaks, but it doesn't really help much. If you want to give a squad a break, give them a break when they start to seem unhappy by inactivating them.
Instead, I would recommend dissolving all squads and creating squads of 2 dwarves. They will then tend to spend their time sparing, rather than running lessons (unless you put a dwarf with superior skills in with a rookie - so try and keep dwarves roughly matched in skill. Dwarf Therapist can help a lot, especially the splintz (? I forget?) version which I think has had some military tasking capabilities added. (Oh look, I found it after all http://www.bay12forums.com/smf/index...117#msg3397117 )
I have quite enjoyed danger rooms. Don't think they are a perfect panacea - you need to keep women out of your military (babies can't dodge even training spears, who would have thoughts?) and pets can quickly be turned to paste if let in. You also want to set up a repeated (a loop of track, pressure plate and a mine cart and a roller work brilliantly). Also, while you will have skilled dwarves they can still be easily machine-gunned down by elite marksgoblins. And hey, it's kinda fun to send your dwarves in rather than sitting back and leaving the traps to do their work. Especially when you know you can train some up again relatively easily.