"Didn't last very long" might be taken as indicating that they were unreliable.

Actually, in the 1980s and 1990s, many Soviet era satellites just didn't last very long. For example, their early Glonass navigation satellites only operated for about 18 months compared to 5-10 years for a similar GPS satellite. They used to launch a lot of store-dump communications satellites (each launch carried 6 or 8 of these satellites). Most of them didn't last 2 years. The fact is, many of their satellites just weren't very reliable back then. They've improved them quite a bit since then.

It's true that many of their satellites were designed for a short life - often less than a month. Sometimes, it was due to the need to deorbit the film for use in reconnaissance analysis. They were relatively slow to field long-lived digitial photo-reconnaissance satellites with a downlink capability and the ones they fielded only lasted much shorter times than ours.

What they did do very well was design simple and effective satellites that were relatively inexpensive. They kept the designs constant and produced them in large numbers, then launched them on a robust family of launch vehicles. I remember reading a classified report in the late 1980s that mentioned a launch failure. They had the replacement satellite on orbit less than 2 weeks later. By way of comparison, the US would barely have the accident investigation started in that time. It would've taken us months to clear the launcher for operations again and depending on the satellite, it might've taken a year or longer to send up the replacement. In that regard, the old Soviet military space program was much more robust than ours and was more closely aligned with wartime operations.