Before you go too crazy trying to stabilize performance with hundreds of forced plans, here are a couple things worth mentioning about plan forcing.
1. I think of plan forcing as a temporary solution. I do not view it as a “set it and forget it” option.
2. Use T-SQL for forcing and un-forcing (versus the UI) so you can track when it was done, and by whom, in change control. Nothing is entered in the ERRORLOG, or anywhere else, and there is currently no event that captures it.
3. Evaluate both the execution statistics (average and total) and the different plans for the query to determine the “best” plan to force.
Erin makes some great points in this post, so read the whole thing.