Chipping in my 2 pennies: my experience is that over time IPA does seem to reduce adhesion. I have been using a mild dishwash detergent for the last few months and find that does the job.
NOTE: do not use fancy body washing soap! It usually contains fragrances and moisturisers which are designed to stay on the surface being washed - which is not what you want.
Ultimately, the objective is to remove any oils that get on the plate and reduce adhesion. IPA does that by breaking down the oils. Soap adheres to the oils.
So with IPA, you may just be smearing lower-order oils across the plate and (possibly) are chemically damaging the plate surface.
Soap molecules bond to the oils and as long as you wash away with clean water, there is a greater possibility of removing them completely.
Dry with a clean cloth (I use kitchen paper).
A final wipe over with a IPA cloth will remove any fingerprints you may introduce when installing the plate.
I guess the next step is a mix of IPA and soapy water. The IPA will break down the more stubborn oil molecules and the soap will bind them up for rinsing away.
One last thought, and something I practice, is to cover my build plate when my A1 is not being used. I cut a piece of heavy card the size of the plate and that sits on the plate to protect against dust, insect poo, splashes and cat paws.