too many sdc constraints?

I've seen that many and haven't heard of it being a problem. It might increase run-time a little, but should be small overall. The biggest concern is managing/verifying them. If the design changes, etc., it can be difficult. I try to wildcard in order to reduce the number of assignments so I can mentally keep track of them. The downside is the danger of capturing something you don't want MC'd, so it's a trade-off.