It's not like he's sitting on the sidelines partying, and taking long vacations. Conor had a 10 month lay off due an ACL tear. He's about to have his 10th UFC fight in three and a half years. Aldo has had 9 UFC fights in 5 and a half years. He's making the UFC, himself and all the other fighters more money.
Everyone who fights on a Conor card makes more money. Fighters should love this guy. Aldo doesn't draw crap. Take Aldo's fight against Chad Mendes. Buy rate 180,000. His fight against Conor, 1,200,000. Conors fight agains Diaz, 1,600,000.
Conor has also already had two camps for this guy. Sparked him in 13 seconds. How motivated could he be to get back in there again and for a third time to train for Aldo again for months at a time. Especially given Aldo's tendency to pull out of fights.
If Conor loses, Aldo gets his big pay day in 3-4 months down the road. He can sit on the sidelines until then. Just stop whining.