increasing the sync interval is not the same as using push. It puts a ridiculous load on the server, particularly if many people do the same.
Push requests send specific items of data after a change, syncing compares with more or less smart algorithms, two databases and tries to bring them to match, which requires significantly more resources and time to do.
Also, when the sync is over, it doesn't mean the server is done, often the chances are committed to the database after the sync connection is separated. Nevermind TCP connection time outs. So you are likely to have overlapping syncs both in terms of database operations and TCP connections.
Further, if you have multiple computers, the chance that they lock each other out increases, because only one computer can sync at any given time.
15 minutes in the past was often to close with four computers sharing the same info, because by the time computer one tried the next sync, computer 3 or 4 weren't done yet syncing the previous iteration.
The result were sync errors, and inconsistent data sets.
IMO, sync more than once per hour, when more than one, maybe two, computers are involved, is too often. 15 min works well with one computer, and the rest being push devices (web, iPhone, etc.)
The problem is, that we don't have push on the desktop yet, but increasing sync intervals is just asking for trouble.