Not to quibble too much, but a Portal Gateway is not a controller -- it's different in a variety of ways.
First, the portal is nothing but a communication device between the lock and the network. There is no intelligence in or no logic executed by a Portal Gateway. This is different than most other wireless locks where there are controllers and if they drop offline, the lock drops offline and goes into a "degraded" operating mode. WiQ will continue functioning as normal if it's offline, but it obviously won't receive updates that are made to the database. Otherwise, you wouldn't be able to tell any difference between a lock that was offline and a lock that was online.
Second, a single portal can theoretically accept up to 64 locks. While I wouldn't ever recommend that many and the chances of having that much density within the antenna range is minimal, that's in stark contrast to other wireless products that require controllers for smaller groups of locks -- i.e. AD400 requires a PIM that supports 16 locks, etc.
You are correct that a high beacon rate will eat batteries, but the question becomes -- why do you need a high beacon rate? If you're working with exterior doors where you need lockdown, then you should be hard-wiring every time. If you're in a high-security environment where the difference between a 15-second and a 2-minute heartbeat makes a substantial difference, you should probably be hard-wiring. It's not a solution for everything, but when it comes to wireless, it's pretty darn good. And, if a customer really doesn't want any controllers (for whatever reason), it's one of the few options I'm aware of. Maybe not the only one, but just the only one I'm aware of.
Just a bit of clarification. :)