I'm going for 99 firemaking the cheapest way possible. Im at lvl 70 now, and im burning willows to 99 since im short on cash. Around about how long would it take to burn 136,308 willows?
As for botting, doing a 24 hour bot and managing to do 40k-60k logs a day seems quite a stretch, and would be an instant ban-hammer or 24 hour non-break firemaking.
Willows max out at around 100k xp/hr burning, so from 70 you're looking at about 120 hours of training, which is 5 days non stop. So if you're botting it will be 1-2 weeks, 3-4 weeks if you play legit.