For me, part of the attraction of the Eco is the ease with which the nib and feed can be removed and flushed - and the (comparatively) low price point. I recognise that this can produce additional wear and tear, and shorten the life of the pen - but it makes it an ideal pen for using my shimmer inks (and I very much enjoy using shimmer inks!).
I would *not* recommend trying to regularly disassemble TWSBI Diamond nib units - the Mini, especially, is wedged in firmly and you're liable to break off a few fins (don't ask me how I know... ). But I'm comfortable doing this with the Eco - and I'd reiterate, unless the OP was being particularly rough, based on my experience with these pens that seems more likely to be a fault in the material. The nib and feed are almost *too* easy to remove and insert - and it's possible to do so without placing *any* stress on the grip section.
I'm familiar with the argument that "Just because you *can* disassemble, doesn't mean you *should* " - and I wholeheartedly endorse it, especially with more expensive and/or pens that are made of more fragile materials. But ultimately that's a call I get to make with my own pens, and with those that (in my my judgment) are designed to be readily disassembled (including the TWSBI Eco, and practically every pen I own from Fountain Pen Revolution), I'm going to make that call!