Not exactly, the date that each episode is aired is meant to be when it is set, or there about (for example they may do a Halloween episode but the air date is 2 days before the actual date of Halloween etc.)

Putting this into account, we know they only air episode between September-May time, we can rule out many weeks of the year. In the last season for example the September 19th to May 14th or 34 weeks. Often they miss out May - September and just fill us in on what happened (e.g. Lily in San Fran, the development of Ted + Stella's relationship). Additionally, then there are obviously times where there is a holiday break (December 5th - January 2nd), where you still have to believe they they spend roughly the same amount of time in the bar.

But anyway, using your logic the 34 week period when they are airing a season would mean that if they went to the bar once an episode it would average out to around 1.4 times a week. BUT then you have to consider other factors such as the time scale of each episode, some spanning a couple of hours some perhaps few days or a whole week). Though lets say that an episode spans across a week, they may visit the bar 3-4 times during the episode, hence, 5 times in a week (1.4*3.5). That doesn't seem that unreasonable for a group of friends that live above a bar.

In conclusion no it is probably average around 4-5 times a week.

Permission to say "Lawyered"?... no probably not, ok then.