Most of the recipes I make regularly started out as experiments as long as 25 years ago. I naturally did plenty of tweaking at first but eventually I dialed in the flavors I liked. I started brewing in the first place because there were specific beers I liked and there were specific profiles I was wanting to emulate. And I was interested in good repeatability.
So, like oscarvan, no tweaking in the sense of constantly changing things up just for the sake of it.
Nowadays any changes to my tried and true beers only happen if I am forced to substitute ingredients for one reason or another. Fortunately, substituting malts, hops, and specialty grains when necessary seems to have little impact by and large on the results I've come to expect from my regular formulas. So really I have no pressing urges or desire to change them up other than what necessity may dictate.