There's nothing to say those three or four novels have to be full length adult works.
By way of example, last year I finally sat down to write the junior SF novel I'd had on the back-burner for a couple of years, and it was so much fun I went straight on to write a second novel in the series ... and half of the third. It was a different experience to writing my adult novels - lighter, more enjoyable ... and quicker.
After a few months of editing I put aside the junior novels and went back to my current adult work ... and what a revelation that was. I usually strive for clean, unvarnished prose with a minimum of description (x10 when it comes to junior fic) but I realised I could easily cut 10-15% of Hal Spacejock book 5 just by tighting up the writing.
And that's why I'm going to suggest the following. If you have one or two adult novels doing the rounds and can't face writing another just yet, why not write a childrens book? I aimed for middle grade (roughly ages 9-12), and my goal was 25,000 words of fast-moving and entertaining reading. I had a lot of fun with it, and it made a nice change from the vastly more complex adult novels with their multiple viewpoints, twisty subplots, and sheer word count.
Most of us have kids, or neices & nephews, or grandkids, or someone in the 9-12 age group. I didn't stress about writing the next Big Thing (as if!), I just pictured a couple of my younger relatives reading the book, and wrote the sort of story I hoped they'd enjoy.
Changing gears to write a shorter childrens book may just give you the tools you need to sharpen your adult works. If it doesn't work out, so what? I told myself 25,000 words was a nice bit of practice, if nothing else.