Both of ours are recall trained, both have gotten loose, and both have returned when called. But I put "not reliable" because I think it's at the mercy of too many variables.
A recently developed variable is age. Spencer may have some mild cognitive deficit due to age and long-term meds; but whatever the reason, he appears not to hear what he doesn't want to hear, to sometimes forget what "no" means, etc. Shane is increasingly a slave to his nose, leash or no leash (back yard). And if you want them to leave the raccoons up in the tree and come inside, you pretty much have to deliver that message in person.
Then there's the issue of one (such as myself) putting effort into training, only to find that someone else (not naming names) has partially undone it while one is sick, out of town, whatever -- because this someone wants so much to be liked!