Varies by base. SFO is about 90% four day trips. Just a few 3 days and hardly any 2 days or locals. I think LAX is similar. Fresno used to have a lot of locals and 2 day trips when I was there.

LAX, PSP and PDX tend to have shorter legs so you get more legs per day and generally lower credit. SFO and SLC have longer legs. FAT is a mixed bag.