If you cast another spell, the touch spell dissipates. (PHB ch. 8, "Magic Actions: Touch Spells in Combat: Holding the Charge")
Creamsteak said:What about if theres a 2nd caster that imbues you with a touch spell? Not sure if theres anything like that, but it seems plausible.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.