They are practically undestuctable, to be honest. Especially earlier batches. The quality is getting worse, however.
The best Vostoks are produced during the USSR period. The problem with modern production Vostoks is that they are poorly oiled, which causes a lot of reliability issues. That's why I have my movements serviced before I use them by a watchmaker located in Russia.
However, I am sure that you can ask Meranom to service your movement as well. Although I do not know how much he will charge. Vostoks quality plummeted a bit after the USSR collapsed. Then the newly privatized firm experienced financial difficulties and went bankrupt if I remember correctly.
However, I believe the company has been reorganized and their tooling has been upgraded. So I expect their quality should not be as bad as the ones produced after the bankruptcy of the firm. I don't like some of their newer lines of Vostok though, such as the Quartz Chronographs with Ronda movements selling for 350 USD.
Still, for a 60 USD watch they are pretty good. However, it does feel pretty bad if you received a watch with QC issues, which does happen ocassionally. An example would be some reports of the reverser wheels being improperly oiled causing autowinders issues.