>>4970891
There is no timeframe per se. A Congressional session lasts two years. Any nominations not confirmed in that period expire. When the next two-year Congressional session starts, the president can resubmit the same nominees or brand new ones.
The problem is 2020 is a presidential election year. If Trump doesn't win again, he could be handing over a lot of vacancies to the next president (probably a Dem). That person most likely will nominate very liberal leftists.
Right now, there are 146 judicial vacancies. Trump renominated 56 (which weren't confirmed in the last session). He just submitted these 7 leaving 83 more to do. A major reason Trump is so far behind is because Dems haven't agreed with his selections for their states/circuits. No more nice guy.