but when I started I was a weekday guy,

 
The reason is that when I started, I had a family at home so weekend were devoted to them.   I have a job where I needed to go hither and yon to meet clients, etc., and so could incorporate a session into my noon time lunch break without arousing too much suspicion.

 
But now I live alone, and being all rested and relaxed on a Saturday afternoon is far more enjoyable than sneaking in a quickie and hoping my cell phone doesn't go off.

 
I have no preference on when an ad runs.   I check out TER 3-4 times a day.

In Vegas I tend to be a weekday guy. I like the KGirls, and I try to arrange a noon or 1pm meeting when they are fresh and usually aren't too busy (and rarely have a 'next guy' stacked up behind me). On the weekends and evenings they tend to be busier and the appointments frequently wind up being 45 minutes instead of an hour.
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When I see indie ladies it seems to be more sporadic last minute dates for me, so it could be any time if they're available on short notice and I'm looking for fun.

I haven't kept a tally of TER replies over all the years but there are plenty of  
"My schedule is such that ..."
"... I am a short notice guy only." AND
"... I need to plan several days or even weeks in advance."  
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If you haven't done so yet, maybe you can keep track of each sort of inquiry you get and correlate it to your ad timing.
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Are most of your inquiries, "I just saw your brand new ad on TER ... Are you available [today? tomorrow? this coming weekend?] or are they "I just saw your ad that you posted a few days ago on TER .... Are you available [now? tonight? tomorrow? ...]
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Where are the Freakonomics statistics guys when you need them?

I look at new reviews almost daily and ads weekly. When I look has no correlation to when I hobby.  Infrequently I will see an add and add the woman to my “ondeck circle”. Otherwise, I always have my next 3-4 targets on the list for the next few weeks. Therefore when you post an ad has no bearing on whether I will see you. Having several favorable reviews posted in a 1-2 week period is more likely to catch my attention. I will click through and explore almost every strong review in a given week. I am asking myself, “is she in my price range?  Is she hot? Are the pics recent? Does she get consistently high ratings? Did one guy think she gained 20 pounds? Did a few reviewers slam her performance? Is she a fit for me? If this query results in mostly “Yes” responses, perhaps she gets elevated to “ondeck”. Timing of post has no bearing on who I see.