Holds for pilots have been the norm since Gulf War 1, when all the instructors were sent back to the front line, and training was stopped. Holding officers are used by some sqn's to help out in undermanned ops/admin posts. The airforce actually "needs" holding officers to do some jobs it has no manpower for.
Sadly, this means double the time to get to the front line. This doubly penalises the pilots, as they take longer to qualify for flying pay, and exit dates are based on reckonable service, which counts from the end of your OCU.
It has been known for guys to hold up to 9 years!! I had a mate complete 2 masters degrees whilst holding.