... I only come here on days that end in "y".  

I check her and P411 almost everyday just to check in and see what my favs are up to. I have to plan ahead for my adventures so just seeing who is out there and available helps in the process.

Early in the week for me

I am usually booking appointments for Wednesday or Friday on Mondays.

Thursday is golf day, and try to go to gym, MWF, so that leaves Tues.  Weekends not good.  However, if a good opportunity presents it(her)self, I will sacrifice the gym, but not the golf...LOL\

LLAP,
Swim

I'll use the forum ads here as an example. I always try to get my ad up Sunday evening or Monday morning. The way I see it, the married gents have been at home all weekend without any opportunity to browse or get out to see someone, so if I have my ad at the top on Monday morning when they come into the office they will see it.  

As far as most other sole advertising purpose sites, I usually just renew it whenever the last one expires.