Dustin Johnson won the 2018 RBC Canadian Open for his 19th-career PGA Tour win, putting him on the precipice of securing PGA Tour lifetime membership.
A PGA Tour player can earn lifetime membership by doing just one thing. If a PGA Tour player wins 20 PGA Tour events in their career and have played on the PGA Tour for 15 years, they instantly obtain lifetime membership whenever they hit both of those milestones. They can never lose PGA Tour status, no matter how they play for rest of their career, from that point forward. They can lose voting rights if they don't play the minimum number of PGA Tour events (15) in a season, but that's about it.
Now, a PGA Tour lifetime member doesn't necessarily mean that player gets into any tournament they want. In terms of the PGA Tour's priority order, which determines how PGA Tour players get into most open PGA Tour events, PGA Tour lifetime members are in Category No. 17, behind the last five winners of each of the four majors, the winners of PGA Tour events and a few other categories. In addition, the majors, World Golf Championships events, invitationals and several other tournaments have their own entry order putting other criteria ahead of the PGA Tour's priority order system.
In other words, having PGA Tour lifetime membership doesn't guarantee much of a schedule, but a player who has 20 wins and 15 seasons of service probably doesn't have that much of a problem setting up their season.
On the PGA Tour, there are currently only two players competing under the lifetime membership category: Vijay Singh and Davis Love III. Other players, like Tiger Woods and Phil Mickelson, have that status but do not yet need it. Love III is the last player to earn lifetime status, back in 2008.