Most porn sites have a download limit or block downloads for trials because it helps eliminate people that sign up for 1 day just to rip all the content to distribute elsewhere.
I would strongly recommend the $5 monthly trials that the big studios do occasionally. A whole month to enjoy the content, I never encountered any download limits, and $5 is pocket money.
I don't like them as most auto renew at full price if you don't cancel in 24 hours. I wouldn't mind them if they had the option to not renew at sign up, rather than having to cancel right after sign up.