Are there any months that are better to visit?

unless you want to also spend time as a tourist. It also depends on how you want to spend your free time.  If you want to do outdoor activities, obviously the warmer months are best.
But I don't think any particular time of year is better for business, horndogs being horndogs irrespective of the season.

I haven't gotten into midtown Manhattan this season. Are the Giant Light-Up Dildoes back at the McGraw-Hill building?

... and Giant Illuminated Butt Plugs?

I don't go into mid-town any more. Also, congestion pricing is about to kick in below 60th St. in a couple of days.

I would think mid-town is easiest for people to get to/ congestion pricing is $9- but if you are already in the city or taking public transportation isn’t a factor- plus if someone wants to see you is $9 going to be deal breaker- I don’t think so - hotel prices are up last year and are pretty high right now - prices are the highest in the spring and fall / then in December for holidays really get high -

Depending on what you find in midtown, don't forget about options in Brooklyn, Bronx, or Queens (sorry Staten Island): offer incall in B, B, or Q but offer outcall to any Manhattan location if the client pays for the round-trip Uber (or sends their limo and driver). Native NYers would have no problem hopping a subway from midtown to B, B, or Q for incall.
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http://www.theeroticreview.com/discussion-boards/new-york-2/the-bronx-is-up-the-batterys-down-people-ride-in-a-hole-in-the-ground--267316
The Bronx is up, The Battery's down, People ride in a hole in the ground ...
See this recent post about getting around in NYC:  
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http://www.theeroticreview.com/discussion-boards/new-york-2/re-any-suggests-267286

I’m a touring escort and visiting often throughout the year and for the most part business is steady except it goes a little quiet in the summer. I am here now and would say business is good but hotel rats are a little higher right now.