A lot depends on how many miles you put on the car each "season" and what you consider a normal oil change interval. I only put 2k-3k on the car each season, I get the car out in the spring, run it a couple hundred miles (to re-suspend all the junk in the oil so it will come out at the oil change), then change the oil. In the fall I just leave the existing oil in it because it's only got 2k-3k mies on it.
'14 F150 4x4 SuperCrew 302
'11 GT MT w/ 3.73s and some bolt-ons 550 RWHP / 490 RWTQ 11.94 @ 123, 1.84 60 ft. Wannabe Sleeper