I'd say yes... with conditions.
I've hit a couple of sites that were probably "touched" by metal detectorists, but not really gridded and explored. For example, out of one small 1/2 acre park, I pulled 17 rings (4 gold, one of which had 3 carats of diamonds), and probably $40 in change. The park was built about 14 years ago. I think it had been "spot hit" by many detectorists, but never really cleaned out. (I did so, willingly!)
I've also hit a high school that probably hadn't been seriously detected in about 20 years. Between my son and I we pulled almost 50 rings out there, with 27 silvers, and 5 golds between us over only about 5 hunts. Well over $120 in change. only 4 fields (soccer, 2 softball, and one practice football field). Amazing experience.
That's the best I've had... Never had anything "old" though. The best part of park hunting, is that give them some time... and they fill back up!
Cheers,
Skippy