In the past 18 months, I've completely disassembled and degreased the range blower, which includes the motor itself. But after a few months of normal usage (it's just a home kitchen after all), grease seems to collect inside of the housing unit and pool up. Eventually, once it has pooled up enough, it'll start to drip out.
Is this normal? Or is it supposed to get trapped more into the filter, which I do run through the dishwasher every couple of months.
Home kitchen hood filters are usually not that good, at least comparing them to commercial hood grease filters (of course, the commercial hood may well cost as much as a used car, or perhaps a new car, and the home hood, not so much.)
If you generate a lot of atomized grease and greasy smoke, some will make it through the filter and be deposited on the components after that point. How often you'll need to clean the hood varies quite a bit with what you cook under it.
You might want to step up the filter washing to every month, or even two weeks, rather than a couple of months. This is entirely cooking dependent so what works for me and what works for you will be different; I clearly fry a lot less than you do, based on your reported required degreasing frequency. But a totally clean, not very effective, filter will still be not very effective, so you might also need to look at cleaning inside the hood more frequently to stay on top of the problem.
The typical aluminum mesh filter in most home hoods is lightweight, inexpensive, and not terribly effective at trapping grease. They are generally claimed to be dishwasher safe, though due to the common interaction between lye in most dishwasher detergents and aluminum, they may discolor. A stainless steel baffle filter is typically more effective, heavier, and more expensive - and may not be available for your hood at all.
In most places the commercial hoods still need to be cleaned every 6 months or so to prevent fires...
Metal filters as commonly fitted to extracting hoods allow good airflow but don't catch everything. I know it's time to wash mine when a drip starts to form under the motor housing, or even falls onto the stove. I've never come across metal filters that couldn't go in a dishwasher, but they probably exist somewhere; hand washing is basically useless. If you usually use a low temperature or eco mode on your dishwasher, it might be worth trying putting the filters through on intensive mode with the maximum detergent.
I clean the motor housing and other accessible bits when I've got the filters off. The grease is a bit too sticky for paper towel so I prefer use a rag or old washing up cloth then throw it away.
Other hoods, usually recirculating ones, use paper filters, or a fleece-like synthetic material. These must be replaced quite often as they're not washable and clog easily. When clogged the fan does no good, just makes noise. I had such a recirculating hood (on an outside wall so there was no excuse) and was glad to get rid of it.
