I haven’t reached level 60 yet, but I will eventually, and because I bought the lifetime subscription, the length of time it will eventually take is no longer an ‘issue’ for me in the sense that I don’t have to worry about using my time ‘optimally’: Since I deal with a low-level but chronic anxiety (called generalized anxiety disorder), eliminating extra ‘worries’ like that was important to me.
And, since I bought the lifetime subscription during the Christmas/holiday sale (which they usually have each year – it’s either on right now, or they will start it fairly soon, I imagine), that means I only paid one time. I forget the original price and discount, sorry; it was over two years ago now. In fact, that purchase price has already ‘paid for itself’, since it was equivalent to roughly two years (or maybe just a bit more) of year-long subscriptions.
I’m currently on level 12, but actually I previously had gotten up to level 28. However, I had ‘rushed’ to get to that high of a level, which turned out to be a mistake overall (see my post about resetting to level 7 if you’re interested in why and how I decided to do that), and the fact that I had purchased the lifetime subscription was a big factor in making that decision much easier: I didn’t have to worry about “Oh! I’ll have wasted so much time/money if I reset! 
” Instead I was able to just think about what’s really important to me: I really do want to learn Japanese, and I want to be able to enjoy the experience while I’m doing it. Having a lifetime subscription separated out any connection between those important goals from any concern about money or time. Personally, I’m very glad I went with the lifetime subscription. Just my own personal experience. Your mileage may vary, as they say.
Recently, around the time I reset to level 7, I found a thread on the forums called 
Let’s Durtle the Scenic Route 
, and since then that’s the perspective/philosophy I’ve embraced going forward. I’m no longer concerned with just ‘playing the SRS game’ to get to ‘level 60’ per se. Instead I’m more focused on my real, main goal, which is really learning Japanese and also being able to enjoy the process as I go. Again, your mileage may vary. Different people will have different goals and different approaches to learning. This is just from my own personal experience.
Hope this info provides a helpful perspective, though! 
Cheers, and Happy Durtling! 
