just wondering if anyone would know how long an I-765 takes while i'm waiting for adjustment of status

Can vary greatly depending on your local USCIS District office. To get an idea look at the timelines AOS section and filter by your USCIS District Office.

http://www.visajourney.com/timeline/

Or look on USCIS website and look up your District office, and see what filing dates they are looking at at the present moment

https://egov.immigration.gov/cris/jsps/ptimes.jsp

Since your profile is incomplete I could not give you a more specific answer. Why not fill in the blanks on your profile and perhaps start a timeline to help others get a grip on how long it takes to get AOS?

Under 8 CFR 274a.13(d) USCIS has 90 days from the date of their receipt of the application to issue you an employment authorization (there are a few categories of immigrants to whom the 90 day rule does not apply). USCIS' failure to comply with the 90 day requirement results in the automatic grant of an employment authorization for a period not to exceed 240 days (it's "automatic" in the sense that USCIS has no discretion but to give it to you; you must still obtain a physical EAD from USCIS before you can work, however).

Now, in the event that your employment authorization application is missing required INITIAL evidence, under 8 CFR 102.2 ( B )(10) the 90-day countdown does not start until USCIS receives that evidence.

Now, if your application is missing anything OTHER than the required initial evidence or if USCIS requests ADDITIONAL evidence, then the countdown clock is simply suspended until USCIS receives such evidence.

To illustrate, if your employment authorization petition has been with USCIS for 20 days, then USCIS requests additional evidence of your eligibility, USCIS will have 70 days to finish processing the application after USCIS receives the evidence. Now, under the same scenario, if the required INITIAL evidence was missing, USCIS would have the full 90 days after you submit such initial evidence to finish processing your application.

Our first one was received June 18, 2004 and the notice date of approval was June 29, 2004. Plus mailing times. Best wishes on yours.