New DLC for free for a limited time:

http://store.steampowered.com/app/204387

Happy Valentines Day :)

Honestly, the longest I've ever spent on a single (non survival) map was about half an hour and there's no problem if you have to leave mid game on most every map (if you aren't building the main defence, but play as hero based damage :p)
So, do not worry about that, I think people would love to pay you company for a map a day, or a week!
And yes, you should drop out instantly if you start to suffer instead of enjoying the game!
As for what Ubivis mentioned, have you tried to set the game to 'lowest' setting, that seriously reduces the amount of light and colour for me (had to take that step with enough explosion and monsters to keep my GPU alive ;)).
The only issue I see is that a hero based character might be considered fast paced, whereas a tower based one could cause some inconvenience if logging out mid game.

I tried before, only can play for less than an hour, if not i have to fight the headache. According to advice that i found in most game booklet, you must stop playing immediately if you encounter such symptom :)
It's not motion sickness, but BPPV. A minor one. The same reason why i don't play much online game. Because i might need to stop playing during mid game, thus not really fair to other people:(

hmm... there must be a solution Wormhole... how about adjusting the color settings of your monitor to have black/white Only? One problemsolved :)

Levels can be beaten easily and quick with the correct tactic.

Fast paced might be a bigger problem :(

This game is great from my observation (watch my younger brother play), but my current state of health doesn't allow me to dedicate too much time in game like this because it's fast paced, colourful, and take lot of time to finish. So i'll easily suffered headache during mid game. Sorry couldn't join you guys.

I have seeen her only 2 times and both times she spawned at the very same spot