Take your time! You've already explicitly mentioned your intent for quality over quantity, but there is nothing better than to have it reiterated so that you can feel rest assured that it's the best thing to do.

While I've never tried any of your levels (well, I suppose I haven't played custom levels from anyone), I'm thrilled at your approach. Mini-mods, in my humble and overtly biased opinion, are cycles better than the mods that try to do everything, because they focus primarily on what's important: the levels. This alone leads me to reiterate: Take as long as your mind and body need to determine the worth of your irrevocable result. I took note of your initial statement that you had released your 25th level to the forums - this was in July. Your level topic was introduced in January, but I will assume you had created some of the levels in prior month(s). So, that's six months for 25 levels, plus a possible seventh or more. To create 50 levels of high quality, based on this information, we're looking at a release sometime next year. But like I said, I don't know what you already have done. But I've wasted all that time speaking of such to say the following:
Don't set limits. Having an initial goal of 50 levels is a good idea, but don't stress to hit that number if you're having trouble getting there. Sometimes you may have writer's block, but at some point you may also get worn out from the work. That's OKAY. Point is, as long as you provide a result, no matter the quantity, then whatever work you put into it will have been worth it.

Obviously I'm a terrible example of a person who practices what they preach, but don't focus too much on my hypocrisy.
I love you, but your attitude is like that of a shrew. Your options? Take a pill or be my kill. Might I suggest that you wear a vest. Perish in class or be banished to the land of bluegrass, where dreams don't exist as you'll be eternally pissed.