From a civilian instructor's standpoint, there's no need to push someone to solo, but there is definitely a point where you should be concerned if they don't.
Since an initial (not add-on) student needs a minimum of 30 hours of dual, 20 hours before solo just means that when they are flying around by themselves, they are more likely to be practicing proper and refined technique and tactics.
I like to solo them later, then let them fly alone for a few hours, just taking some quick dual flights to be sure they are still on track. Then when they've got all the solo RQ's out of the way, we spend the last hours polishing the advanced maneuvers.
I've noted in highly unscientific surveys that time to solo in the civilian world (if within the 10 - 30 hour range) has little bearing on time to checkride. However, if you get someone who is going beyond 40 hours to solo, it's time to get other folks involved, because that pilot's ADR*.
*ain't doing right