Right before the game had come out, they offered lifetime subscription. I was not one who could afford it at the time. I wish I could have, but I could not at the time. I though down the line, did get my lifetime when I did finally have the money to get it. With a year or two, depending on how much you spent on it, depends on how long you will break even.
To me, a lifetime is well worth it if you are going to play the game for a long time. Even if it ever goes free to play, it will still be worth it as long as they give you a monthly credit to the cstore. One of the advantages of the lifetime I had found is that I do not have to worry from month to month if I have the money to pay for it. Some months, you may be short on money for whatever reason. This covers that.
You do not get many perks, but the best perk of them all is not having to pay month to month. You do get to make up a liberated borg. You do not get extra character slots just because you bought a lifetime like what you did get at the beginning. That was just a way before the game came out to get some people to buy the lifetime subscription. You also do get access to the captain’s table which is nothing special and you do get career officer for the STO forums.
In closing, I feel that this is well worth it if you are going to play for a long time.