If I drove 20k+ miles a year, I'd absolutely do a 20k interval with a UOA to verify. But at the rate I drive, it'd take nearly 4 years! LOL.
I drove 25k last year with my Land Cruiser, I expect 30k this year, I use Castrol Syntec 5w-30 and change it every 5k because there are also 4 u-joints, 2 slip yokes and ball joints and tie rod ends that need to be greased.
I would never go 20k on a single oil change unless I had a 8qt or larger sump and drove unladen on the expressway all day long.