Why did the Soviet Navy appear cautious about overseas bases?

Was Soviet caution about overseas naval bases caused by cost or fear of losing control?

The main constraint was opportunity: the Soviet Union took bases when access was available and used them to exert local control.

Opportunity is the main constraint proposed for Soviet overseas bases. The Soviet Union was willing to acquire bases when access became available and used them to exert control over the surrounding area. Eastern Europe and other aligned countries supplied examples of extensive basing. Cost and fear of losing control are alternatives raised by the question, while the explanation adopted here emphasizes access.