lower pressures will lead to sidewalls wearing faster than at pressures above 35psi, as the sidewalls will flex more. If you ride in rocky areas you may find this is a problem, if you dont then it may not be an issue.
all below were run on the rear wheel, Stans no Tubes at about 20-25 psi, in abrasive rocky terrain (on either a 7″ forked hardtail or a 7″ full susser).
1- I ran a non tubeless Maxxis Minion rear 2.35 single ply (quite flimsy sidewalls) and wore the sidewalls out (to the point of being able to stick a tyre lever through the cuts in them) in 4 months.
2- I then got a dual ply non tubeless DH CASING 2.5 Maxxis Minion non tubeless, lasted a few months more than the single ply but the rubber rubbed off the sidewall outer surface and they needed a bit more sealant to seal them again. worked ok but more hassle.
3- tried a bontrager 2.5″ Big Earl tubeless ready. The sidewalls were virtually unmarked after 4-5 months riding at the same pressure as the maxxis. The tread however was totally worn off, where the maxxis both had a fair bit of tread left on.
My verdict – UST/tubeless ready tyres are the way forward for low pressures due to the abrasion resistant sidewalls. Otherwise stick to slightly higher pressures, or accept that tyres will last only a few months.