I usually pass on review offers mainly because the first chapter was drawn early 2015 and the other one early 2016. I'm currently working on the third chapter and it feels like I've upped my game a lot since the last two with pacing, panel placements etc that it feels a bit irrelevent to get critique on my older stuff (like, people will point out stuff I already know are so-so, and that it'll be fixed in the next chapter).
However, if I'm unsure of stuff, like dialogue, flow, etc, I'm usually asking for advice on that certain piece before I go live with a page, and I usually let people proof read the chapter =)
But yeah, I should probably be more brave and ask for reviews, but it IS pretty scary! I put so much of my free time on it, it's hard to not take it personal, I guess ^^; But also, you could miss out on an opportunity to get a really nice review and good exposure, I guess? :3
Speaking of, I got this nice review on my webcomic, and it made me so happy and really willing to keep going and make the comic even better <3