geewiz,
so far I have had to divert 5 times (3 'crash' 2 weather)
2 x for collapsed landing gear, in each case it took way longer than 15 minutes to cleanup. Once I was in the crew room of the diversion for about 5 hours and once I did my whole BFR and then dropped the examiner at a different airport while they departure airport remained stubbornly closed.
In general in a spam can I wouldn't particularly plan a crash diversion unless I was in a particularly sparse airport area, the circumstances will always be different and my aircraft can get into most airports. If I was flying a G6 on the other hand.... (just wishing). On weather, I would plan something either local with an ILS if going into a VFR field or something in a different weather system (having made he mistake of not doing that, going missed at primary, then at alternate, and then needing to formulate a further alternative plan - fortunately with 600nm of remaining range)