What’s the consensus on purchasing 4 inch filters…big box or mail order? I have two furnaces, which for twenty years used a Honeywell electrostatic air cleaner that had washable filters and they worked great. When I updated both HVAC systems two years ago, the electrostatic air cleaners were on their way out, I opted for the replaceable 4 inch filters. I have been purchasing them from the big box store twice a year, but I believe mail order might be more cost and time effective...if they get delivered undamaged. I’m thinking of nordic pure with free shipping, anyone have experience with on-line filter ordering?