Well, at flybe:
Home standbys are generally either six or 8 hours long. My roster tends to have 2-3 standbys a month maximum and I'm very rarely used. The early standbys are usually 0400-1000L and the later ones anything from 0700-1500L to 1200-2000L.
Airport standbys do happen however I personally haven't been rostered one for about 6 months. I think they've more or less disappeared completely in my base (one of the large and busy bases). Their maximum length is 6 hours and when combined with a flying duty the total duty time cannot exceed 8 hours.
Hope this helps
P.S. we certainly don't have a surplus of aircrew at the moment with start of the Greek operation. In fact, there is the possibility of slight recruitment if a few things work out.