Series That You Wish You Didn't Start?

I am looking for a new set to do and this thread has been really helpful on figuring out what ones to steer clear from. I have started a few sets (my progress is in my signature) and have not regretted any so far.

To each his own.

I started my collection as a teen with the goal of one of each type of circulating world coin. The fun is in the journey.

I don't regret anything I've started myself, but somebody gave my son a (extremely) partially filled Whitman Buffalo nickel folder at a coin show a few years ago and I sorta wish that hadn't happened. Gone are the days when you can find Buffalo nickels in circulation and have a hope of completing a set over time that way. Instead, the only way he will ever fill in this album is if I (or he, when he is older) go out and purchase every single coin.

As much as I am not personally a fan of collecting currently circulated coins, I will say that one nice thing about collecting them is that it's actually possible to complete a set in a timely manner. My son's collection of State Park quarters may not be worth anything over face value, EVER, but it was fun to put together and ultimately doable. Same thing for his ongoing collection of ATB Quarters.

I have well over 100 Whitman Classic Albums and mostly all full. However out of all of them there is one I really never should have started. I've had no problem finding almost any coin at coin shows. By me we have about 4 coin shows a Month and some are really big. Yet there is one coin I never should have started collecting. The Sitting Liberty Dime. Everything else is possible but what I never realized about certain coins is the amount minted during the Civil War. At coin shows when I ask why so little amounts of those I always hear that not much is around due to the Civil War. And the little coins made during that time just not many left.
And the same is sort of true with all coins minted during that time.