25 to 40 years ago (yes, my first Vegas gambling visit was in 1976), it was once every year or two for a national pool tournament (I used to play a little) or a wedding, or at least twice when a friend said "hey Bob, I'm driving to Vegas tonight, wanna go?" and I went...13 hours later we'd be there.
I started making it a focal point of being in Vegas for the Super Bowl in the mid 80's, and I made it out there at least 15 in a row for that event. If you like football, Las Vegas is the BEST place to be for the Super Bowl if you aren't actually at the game!
I had wondered what New Years weekend in Las Vegas would be like, so my first New Years in Vegas was the first millennium (1999-2000). That weekend was three months into my 18-months-in-a-row trips to Las Vegas. I was also there for the second millennium celebration (2000-2001).
That 18-month stretch of flying to Vegas at least once month afforded me a view and actual experience of the city under just about every setting. The city is different when different things are happening in the city. I won't ever go back for New Years. Twice was at least one time too many.
NASCAR week (last week) can be fun if you are into NASCAR racing. I had media credentials and an infield parking pass for the inaugural NASCAR event at LVMS locked up before the Las Vegas casinos, rental car agencies and airlines servicing Las Vegas knew what was happening there. I got a cheap flight, a cheap room, and a cheap rental car reserved within minutes after NASCAR made the official announcement for that event. Within a couple days, everything got stupid expensive. Las Vegas literally ran out of rental cars that weekend! The city is used to accommodating several hundred thousand visitors at a time, but most of those folks don't need to rent a car. When 80,000 or 100,000 people want to go to a site that is not downtown or on the strip, cabs get real expensive!
These days, I go to Las Vegas for work at The Strip at Las Vegas Motor Speedway, NHRA Drag Racing, usually April, sometimes October. I also try to attend the CCGTCC (Casino Chip and Gaming Token Collectors Club)convention at the South Point in June.