factors in a longer-than-average primary?

hi everyone,
thanks so much to all the kind responses to my previous questions.

a few times i have noticed primary going quite a bit beyond its average 2-3 days...
i know factors such as
underpitching
cold temps
lager yeasts
can extend the primary fermentation a bit, but what might be some other causes?

i have an ipa going on 6 days, made with 1056 and a 3 pint starter at 70 degrees.
i also had a wit go moving and bubbling for 2 weeks, wyeast wit yeast.

any thoughts?

Available nutrients, oxygen level of the wort at pitching, and yeast strain will all make a difference.

The Wit strain in particular is a very sllloooooowwww fermenter at 70*F or below but has no trouble finishing in 6-7 days at 72*F or warmer.

the ipa is STILL going (movement and bubbling) 13 days later?????