There is no "infinite XP cheat" in Fallout: New Vegas. The game's mechanics prevent infinite XP exploitation.
While some perks or glitches can speed XP gain, they aren't true cheats and aren't guaranteed to work permanently.
Consider modding to enhance XP gain. Many mods modify XP rates or allow faster leveling. Use reliable mods from reputable sources to avoid bugs.
Best way to enjoy Fallout: New Vegas is playing as intended—explore, make choices, embrace challenges!