I do see value in occasionally pushing up against my comfort zones. Not in a punishing way, like enduring all manner of shit because it's supposedly good for me, but rather like a periodic testing to see if the parameters of my comfort zones have shifted, expanded, or contracted.
I mean, there are a lot of foods and condiments I like now that I told myself I hated as a kid without even trying them. If I hadn't ever chosen to bump up against my self-imposed limits, and to actually try these things, I wouldn't be enjoying yogurt, coffee, mustard, and some other things as much as I am today (yes, these are all foods that I never even tasted until I was an adult). I still wrestle with feeling awkward around people, especially in group settings or parties, and so I push my comfort zone a lot to get past that because I do want people in my life and to be more at ease in groups without needing alcohol, so I am willing to look foolish and feel uncomfortable to achieve that goal. But if I ain't feeling the need to go there, I guiltlessly stay home and enjoy my comfort zone.
I approach the boundary-testing of my comfort zones as an exercise that I do solely for my own benefit, if and when I see fit to do so. If I find that I like my comfort zones just as they are and have no need to push past them anymore, that's perfectly fine, too. But while I do think that it is beneficial to at least look at our comfort zones and occasionally test them, I don't think anyone else should be telling me which comfort zones I should give up or test - and I hope I haven't come off as someone who tells others what zones to test, although I know I've made suggestions to people as ideas to look at and see if it rings true for themselves.
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein