How long does it take for the EB-5-based I-485 to get approved?

If your priority date is current you can apply to adjust and for March can file under Chart B. Cases are taking at least one to two years to adjust in the U.S.

In order to know when you can file an I-485 so as to adjust your status in the U.S., the best source of information is to check the Visa Bulletin on India. This should give you an idea when you can also simultaneously file for an EAD since it goes together with the I-485. Advisably, in the meantime, stay on your H-IB until you file both I-485 and I-765 for EAD, and even more so, until the EAD is approved.

At least a year but it depends on where you live.

Adjustment of status applications can take from 8 to 15 months. Processing times fluctuate periodically.

USCIS estimates current processing time at the Texas service center to be 8 to 24 months, and at the California Service Center to be 5 to 50 months. It seems the high end of that scale considers those concurrently filed I-485s that have to wait until the underlying I-140 is approved (concurrent filing is not available for I-526s).

The last one I did took under 30 days, but I would guess six to 12 months is normal.

Look at the processing time for the district office closest to your residence. The priority date also must be current.