Through Google, I found various links in other community forums posted by members lik you and I, obviously mostly in Indian based forums, so they are not official. Below are the results, with one USCIS FAQ link. Mostly there seems to be consensus on this particular answer:
Quote
...time limit is written on your petition Approval notice (I-797B) valid from 'start date' to 'End date'. Yes, it's true there are no time limits but if you do not Enter USA within 3 to 6 months then you have to give valid answer at Port Of Entry. Bet of Luck.
Unquote
Links:
http://redbus2us.com/h1b-approved-%E2%80%93-when-to-apply-for-visa-stamping-when-can-you-enter-usa/
http://www.ustraveldocs.com/in/in-gen-faq.asp#qlistwork
http://www.immihelp.com/visas/h1b/h1b-visa-general-faq.html
http://www.immihelp.com/forum/showthread.php/68817-H1-visa-validity-before-travel-and-after-stamping
http://www.immihelp.com/forum/showthread.php/45591-After-h1b-stamping-at-US-consulate-india-how-late-one-can-enter-US
https://www.quora.com/I-have-got-H1B-stamped-from-company-A-in-Aug14-but-did-not-get-the-opportunity-to-travel-so-far-I-am-still-in-India-Can-I-go-for-a-visa-transfer-If-I-resign-from-company-A-and-join-to-company-B-after-visa-transfer-is-there-any-legal-issue-in-doing-that
Follow up questions (for introspection), not necessarily to answer here.
a) Will you still be working for your employer when you are in Nepal?
b) Does your employment start from October 1st, 2016 based on successful H1B visa petition?
c) What is your argument to the Port of Entry officer who might ask you to prove that, with a 6 months gap, you are still employed at the US Company, when you were in Nepal?
