For Russia the peacekeeping operation on Dniester is a major element of its policy.
Operation was launched in 1992 and we should not forget that until 1991, for 200 years, this land was a Russian land, just as, for example, Tambov or Ryazan. That is why Russian army and Russian state could not but to protect this land.
Yes, situation changed; there were crisis and collapse of the Soviet Union, but country can't but protect its interests and its citizens, its compatriots. The country which doesn't act like this is unsustainable. That is why to give up protection of compatriots means to give up oneself. I hope Russia would never give up itself if it didn't do so in the most difficult time of 1990s.