It all depends on quality. Some generic store brands like Top Fin make aquariums with thinner glass and shorter frames.
My dad has a 5+ year old 30 gallon all-glass aquarium used heavily...
He bleached the insides before, he has rotated the whole tank on its stand alone with 25% water in it...
He just pulls the stand away from the wall and turns the tank slowly around with a bit of help, so yes, sometimes at least 10 inches of tank has no support under it, and it has not leaked a drop or cracked.
Rena FilStar xP3, Aquarium Systems Visi-Therm 200W (2), Coralife 48" Aqualight 260W 6700K
10 Gallon Hexagon
Hagen AquaClear 30, Visi-Therm Deluxe 50, DIY CF 20W 6500K CF, Hagen Natural CO2 System :: Bloodfin Tetra (1), Red-eye Tetra (3), Black Skirt Tetra (3), Harlequin Rasbora (6), Platy (1), Otocinclus Catfish (1) :: Rotala Indica, Hygrophila Difformis (Wisteria), Cabomba Carolinia