HVAC and Filters

[GPnative]

When we moved into our house there was one of those reusable/washable blue fiber filters in the single air return for our HVAC system, best I can tell from Amazon it has a MERV rating of 4.  I left it and wash it every few months, it does accumulate some funk. There is also a filter at the air handler, it is a reusable/washable one but it is a metal mesh type filter, multiple layers of mesh. With all this smoke I changed the filter at the air handler to a higher rated disposable allergen filter, mid grade, advertised to help filter smoke. Of course the trade off with the higher rated filters is increased air restriction. Our system so far, 24 hours in, does not seem to be negatively impacted or "working harder" with this higher grade filter in place.
The question, Is the filter in the air return even necessary? Like I said, it was there when we moved in so I left it. But the internet consensus seems to suggest you do not want filters at both locations due to the added air restriction taxing the system and operating less efficiently.
Should I ditch the filter in the air return? Do any of you folks with central heat/AC systems have filters in both locations?

My thought for leaving it is it helps cut down dust from accumulating in the return air duct. But, the system is older and I want it to last so my thought for removing it is so the system does not have to work as hard, especially while this new allergen filter is in place.

[tvguy]

When we moved into our house there was one of those reusable/washable blue fiber filters in the single air return for our HVAC system, best I can tell from Amazon it has a MERV rating of 4.  I left it and wash it every few months, it does accumulate some funk. There is also a filter at the air handler, it is a reusable/washable one but it is a metal mesh type filter, multiple layers of mesh. With all this smoke I changed the filter at the air handler to a higher rated disposable allergen filter, mid grade, advertised to help filter smoke. Of course the trade off with the higher rated filters is increased air restriction. Our system so far, 24 hours in, does not seem to be negatively impacted or "working harder" with this higher grade filter in place.
The question, Is the filter in the air return even necessary? Like I said, it was there when we moved in so I left it. But the internet consensus seems to suggest you do not want filters at both locations due to the added air restriction taxing the system and operating less efficiently.
Should I ditch the filter in the air return? Do any of you folks with central heat/AC systems have filters in both locations?

My thought for leaving it is it helps cut down dust from accumulating in the return air duct. But, the system is older and I want it to last so my thought for removing it is so the system does not have to work as hard, especially while this new allergen filter is in place.

  I think the only part that will work any harder is the motor for the squirrel cage fan. And it you had to replace that a little sooner because it's under more of a load it would not be an inexpensive fix.
I would leave both filters.

[GPnative]

That's what I'm thinking. If It appeared to me that the system was having problems or not keeping up with demand, I may need to make adjustments, but it seems to be running fine.

[tvguy]

That's what I'm thinking. If It appeared to me that the system was having problems or not keeping up with demand, I may need to make adjustments, but it seems to be running fine.

It should be OK. Think about the load on the motor and I doubt it's a lot more with the extra filters than without.
Just think about all the motors who spend their whole life under a constant and heavier load and still last for many years.