Actually, crafting has a 300xp-per-mat-used cap.
I'm convinced harvesting has a cap as well, just nobody's ever hit it. But the cap is a safeguard against exploits, so they wouldn't leave harvesting without it.
I'm convinced harvesting has a cap as well, just nobody's ever hit it. But the cap is a safeguard against exploits, so they wouldn't leave harvesting without it.