Sure. But it's rare with generals, though I remember both Lee
Hsien Loong & George Yeo holding the rank after leaving the
SAF.
There's a few reservist Colonels around, at the brigade
level.
NS officers can be asked to serve until they're 50 years old.
Typically, an ops-ready BN will finish its cycle when its troops
reach about 35 in age, so any KAHs who get recycled will have to do
it a few times to eventually wear the extra crabs.