It probably matters more with some cats than others - those that food spike and/or are carb sensitive. I have been free feeding my entire crew for so long that it either doesn't matter or I have worked around it.
There are some here that think it does matter a lot and I think the TR protocol would say don't feed after +10. One thing that is important is knowing if a rising number at shot time is dose fading or a food spike. With lower numbers you don't want to be shooting a food spike, you want to be shooting a rising number that is indicating the last dose is on the way out.
Another case where ECID, IMO. So gather ye data and decide what works for you.