I have a Carrier Infinity system and was using Honeywell MERV 12 filters without much of an issue, lasting about 6 months. I switched to Filtrete 1550 (16x25x4) and got a "dirty filter" notice on the controller after about 2 weeks. Seemed odd so reset the filter and the notice came back two weeks later. I replaced the filter (only because pulling it out destroyed the filter as it didn't have any tabs to help pull it out of the slot) and it looked somewhat dirty, but I know you can't tell just by looking.
After replacing, I looked at the static pressure:
Low speed - 525 cfm - 504 rpm - Static press 0.16
Med speed - 792 cfm - 681 rpm - static press 0.28
High speed - 1194 cfm - 1022 rpm - static press 0.63
We run the fan on low continuously, but did before with the Honeywell filters. The pressure seems really high. My HVAC guy gave the generic "just replace the filter" response but was not knowledgeable about the actual pressures and didn't even realize that the Infinity system uses pressure to detect when to replace the filter, rather than time.
Should I switch filters again (maybe I can ebay the Filtrete filters)?