Taken from our rules.
Farm Roster Eligibility
Farm roster eligibility is determined by the cumulative total of NHL games played in an individual player?s career. Current eligibility is set to a career total of 50 NHL games (cumulative across multiple seasons):
0-49 career NHL games played = eligible for Farm Roster
50+ career NHL games played = not eligible for Farm Roster
3.5.3 A player eligible for Farm Roster allocation may remain as a farm designate beyond their 49th NHL game provided he was placed on the Farm Roster prior to his 49th game.
Example: Player A has 45 career NHL games played. He is farm eligible. At the start of the 2014/15 season, Player A is placed on the Farm Roster. Player A may remain on the Farm Roster for the entirety of the 2014/15 NHL season (82 games). The player will not be considered eligible for the Farm Roster during the 2015/16 NHL season thereafter as total career NHL games has exceeded the Farm Roster threshold.
3.5.4 A Farm Roster player may be called up to the Active Roster at any time, but cannot be returned to the farm roster in the same NHL season. As long as the eligibility for assignment has not been passed (50 or greater games), a player may start multiple seasons on the Farm Roster.