Even some particular tasks require getting up to speed, even if you have been doing other modeling tasks. One such is ship rigging, especially tying ratlines. If I haven't been doing it for a few months, the first half-dozen ratlines takes an hour or so- once I get up to speed I can wack out a couple dozen per hour, though I frequently limit myself to a half hour at a spell.
You can get rusty at airbrushing, carving and a number of other tasks. Being aware of that, you can allow extra time and lower your expectations for the first few sessions of that task.