Conventional vs synthetic 2010 4.6l

I've been looking around and most of the stuff I can see about this debate is fairly old, or it's people arguing about it lol.

Trying to figure out if it's worth moving over from conventional to full synthetic.

i've got a 2010 GT, been changing conventional every 3-4k miles since i've owned it. It's at 78k miles atm, bought it at about 50.

I've also heard people saying that if it's gone this long on conventional you shouldn't switch to synthetic. And vise versa, when you go to synth you shouldn't switch back.

I already know about the increased intervals and everything. But i'm wondering if it's worth the bit of extra money to switch to it in terms of longevity.

I live in Houston, TX as well so temps can get up there.

would appreciate any input!