The FCC says that until you’re asked to move, you can stay on your 600 MHz Band Channel— which could be for many years.
The FCC last week clarified that LPTV and TV translator stations may remain on their existing channels in the 600 MHz Band until they are notified that they are likely to interfere with a forward auction winner that is ready to commence operations. This could mean continued operations for many years until wireless licensees commence operations. Technically, it could mean forever.
The clarification is in paragraph 60: http://transition.fcc.gov/Daily_Releases/Daily_Business/2017/db0413/DA-17-314A1.pdf
The 600 MHz Band wireless licensee must give LPTV stations that are likely to cause harmful interference written notice to cease operations at least 4 months prior to the date the wireless licensee intends to commence operations.
If a wireless licensee pops up in your region, but “harmful interference” is still not likely (i.e., via Longley-Rice predications), you can stay on the channel.
There is one exception to the exception: Channel 38 does not appear to enjoy this freedom. FCC rule 73.3700 (Post-Incentive Auction Licensing and Operation), says LPTV stations may continue operating on the guard band channel (38) only until the end of the post-auction transition period, and possibly earlier, if you receive notification from a new wireless licensee.