I think a very short period is reasonable.
This is because unlike "posts", we do not keep a publicly accessible (in fact, not even a moderator-accessible) history of comment edits.
5 minutes is already a pretty long time on the internet.
With a longer period I see at least three problems:
Do not cross the streams! The conversation in the comments can get harder to follow, as users re-write their comments rendering other users' responses non-sequitur. In the case of posts the reader can look at edit histories and decipher the progression somewhat. For comments all hope is lost.
Spam spam spam spam! (Remember that edits are not moderator-accessible, unlike deletions!) A user posts something objectionable, and edits it out within 15 minutes. Another user sees it, flags it, and when the hapless moderator wanders by because of the flag, he sees absolutely nothing wrong...
How long is long enough? You suggest 10 or 15. But what is there to say that if the limits were 10 or 15 minutes to start with, you (or someone else) wouldn't have wanted half-an-hour?
As a side-remark: comment preview has been status-declined since time-immemorial, and pretty much all proposals for such have been closed as duplicates, so I am pessimistic on that front.
A few tips and tricks:
Don't put in really long comments. If your comments is getting long and hard to proof-read because of the large number of LaTeX expressions used, consider breaking your comment into several parts and post the parts piecemeal. Shorter comments and LaTeX expressions are easier to proofread, and the five-minute rule becomes more reasonable. (Remember, the five minute rule was originally designed for short, pure text comments on the first SE2.0 websites.)
Preview your LaTeX elsewhere. If you just worry about your LaTeX expressions, you can use anything which supports previewing/compiling LaTeX math expressions to do a preview. This includes the answer-box below the question, the "ask-question" page, our formatting sandbox, numerous online services, and off-line software bundles. For the rest of the formatting issues, the comment boxes uses a simplified markdown syntax, so you can mostly check it with the answer-box.
Considering posting an answer. If you have a lot to say. And they are very pertinent. Maybe consider posting it as an answer? If you don't feel like it is enough of a definite answer, you can always preface it with a disclaimer to this effect. If you don't feel like you deserve credit since the answer is incomplete, you can always mark the answer community wiki.