One of the biggest scammers, founder of incentria, clicksia, earn3, extra10, buxout and earnmoneyspace proved, with the waiting line feature, that long payment delays mean lack of funds. A "bux" site cannot pay more than 10-15 standard members everyday (average 3-5). FYI 60 business days are ~85 calendar days, almost 3 months. Usually within 90 days are being paid less than 500 members, while site can have for example thousands members!
Another scammer, owner of taketheglobe.com, with the same waiting line feature verified this statement.

Long payment delays mean that a site is trying to find money from bot/premium sales. Remember that advertisers are... absent! When site has problems (ponzi schemes will not last forever) payment delays are getting even longer, even and more than 60 business days. Poor reasons will be invented, such as "we have to double-check accounts, many users are cheating", "admin had an accident/is on holidays etc and will be back next week/month" and many more... And of course site has problems because members stopped investing, so simple! Finally site dies and owner can start a new one, using the same recipe.

Instant payments?
The truth is that instant payments are too risky. Only neobux.com seems to be safe from hacking attempts, because a team of programmers is working on site's security. I am sure that all members do not have problems with non instant payments, but with max delay 3 days. Remember, when you are investing you are paying them INSTANTLY. But most of them (if have such intentions) will pay you after months!

PTC sites which need to pay more than 3 days are unstable and will die soon or will turn to "bux.to" schemes.