Computational power required for a route flap is not the issue here.
Many people have stated that, statistically longer prefixes flap
more. Unfortunately, they have then said that because of this shorter
prefixes should have looser dampening parameters put on them, when
what they really meant was that the longer prefixes should have more
strict dampening parameters put on them. Yes it is exactly the same
thing, but it is an important semantic distinction. If a group of
prefixes categorized by a its length tends to flap more than the
average, then said group should have more strict dampening parameters
placed on it.
Statistics are soo much fun.
From a single data point on my router, /24's currently account for 64% of
the routing table entries and for 65% of the flapping prefixes. /16's
account for 12% of the routing table entries, and 10% of the flapping
prefixes. It doesn't appear to me there is a significant difference
between flap behaivor of long prefixes and short prefixes. There are
more long prefixes than short prefixes. But as a group they both tend
to flap the same proportion of 2% of the routes within the group.