if you want to travel recently with soon to expire h1b,

I recommend you either do it long before your travel date, or file the extension after you come back.
it doesn't matter if the expiration date is close to your returning date. once you get here and file it, you have 240 days to work legally without travelling.

worst case senario:
if your h1b extension is approved days ealier than your entry date to US, your latest I-94 would be effective, so you have to file another h1b extension right away