There is NO hard-set "Force draw after X years of 'no progress'" rule. I just want to clear this up, since people have occasionally thrown this around thinking that it's some sort of hard policy and/or that they could rely on that for setting up a premature draw.
The simple reason is that a simple "X years of no progress" rule is fundamentally flawed. Here are just a few examples:
1) Sometimes it take more than X years to perform maneuvers (e.g., bringing new units to the front, swapping out fleets for armies or vice-versa, rearranging lines/alliances, etc.) in order to set up a forced-win or other position that could change the course of the game (such as being able to safely reduce the draw). Blindly applying such a rule could turn some forceable-wins, solo-races (tossups), or even just reducible-draws into prematurely drawn games. This is an important distinction since it means the difference between a win and draw in the situation of a false stalemate that only takes X+1 years for another player to outmaneuver and break down.
2) How does one even define "no progress"? Simply looking at the ownership of SCs does not take into account the possible maneuvering toward setting up a potential breakthrough, nor potential diplomatic progress toward realigning players and breaking down lines. Sometimes, a leader might even regress by drawing away from the line in order to encourage a draw reduction from the other side.
3) Sometimes, we might even be compelled to act quicker than waiting for X years to force draw. For example, in the case of a live game where it's confirmed that someone is simply waiting for an NMR to break through an otherwise solid stalemate.
When it comes to complaints about a game needing to be force drawn, we handle them and decide what needs to be done on a case-by-case basis. Occasionally, we do force-draw a game when a strategy of refusing not to is being severely abused. However, in most cases, it usually does not have to come to that. Ironically, we also get a significant number of premature force-draw requests.
Fundamentally, a game that ends in a draw is quite different than a game that ends in a solo. Solos occur due to the hard-set rule that taking 18 SCs achieves a victory. Draws, on the other hand, require the remaining players in a game unanimously agree that the game should end in a draw (or at least accept that outcome over continuing the game). In general, players are (and should be) allowed to attempt strategies toward obtaining a different outcome should they not accept the draw that others may be voting for. However, there are of course limitations in what should be considered fair and acceptable strategies. For example, things that would not be okay would include (but is not necessarily limited to) waiting for CDs/NMRs to change the position, or simply refusing to draw in demand that other players concede. If you think someone is attempting something along those lines, email the moderators and we will try to resolve the situation. Other than that, I think we have to be fairly flexible about allowing players to attempt reasonable strategies toward changing the outcome of the game, even if those strategies may be somewhat far-fetched. Also, at the end of the day, the game is diplomacy, and the responsibility of convincing a hold-out to accept the draw primarily falls upon the players involved. This is usually done by demonstrating (either verbally or through the position/moves) that a statemate line is or can be established. Of course, if a player is still holding out after being thoroughly demonstrated that other outcomes are not possible, then that could likely warrant a force draw, but it could also mean that they might have a course of action that you might not have foreseen (e.g., maybe they see a hole in your (false) "stalemate" line, maybe they are hatching a plot to take you out of the draw, etc.).
TL;DR: We do sometimes force draw games, but it's done on a case-by-case basis and there is NO hardset X-year rule.