I don't think the problem with getting the notice to replace your filter is with the filter. I also have an Infinity system. I have been getting erratic filter usage readings from the T-stat for several years since it was installed. For example, with the 4" Merv 12 filter ( 20x25x4) being less than 2 months old, I got the notice the filter usage was 100% and to replace the filter. I ignored it. The next day it dropped to 10%. Days later, it was back to 100%. I ignored it and it dropped back to 10% for weeks. Occasionally, it later varied between 30% and 10%. This made no sense to me.
The original T-stat had been replaced within a few months after the unit was installed but it did not help. A few days ago, they replaced that T-stat with the new SYSTXCCUID01-V-25. It started out at 0%, but by the 3rd day it had jumped to 10%. I think something other than the filter is causing the T-stat to not read the static pressure correctly (and therefor filter use). It seems that the % of filter use would progress from 0% to 100% at a reasonable steady rate, not jump around.
My HVAC company is coming out next week to take a look at the duct work to see if something else can be done to solve this problem. Also, I was watching my neighbor's house while they were on vacation last week. They have an Infinity T-stat. They had just put in a new filter. It first showed 10% filter usage. A couple days later, it jumped to 30 or 40%. Couple days later, it went back to 10%. So I just think these Infinity T-stats are just giving out incorrect filter usage information. Exactly why, I don't know yet.
After putting in a new 4" filter last week, here are my CFM, Static Pressure and RPM readings:
CFM S.P. RPM
Hi 1957 .67 1118
Med 1307 .31 775
Low 875 .18 541