After 10+ years of daily Flight Simming, I have less than half a dozen downloaded Aircraft in my Hangar at any one time.
I only keep the aircraft which I use regularly, any more is just a waste of space....and makes it difficult to locate the few I really want to use!
I delete unwanted/unused aircraft, but ALWAYS keep their Gauges, Effects, etc, in case they are required elsewhere...

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My Default Beech Baron 58 Twin tourer, and my downloaded Cessna 150 Aerobat run-about, satisfies most, if not all, of my daily needs...
....and my little Flexwing Trike fun machine!...

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If it serves my immediate purpose, I keep it. Otherwise it is deleted!
Any more is superfluous to requirements...

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F....G-BPLF... 8-)...!
..as much of my time is spent on on-line FS 2004 flights, the use of MS
default aircraft only is obvious!..

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Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.