To enjoy your model collection at its best you will need to display it, the problems with displaying your models are as follows.
Dust causes damage in a few different ways,
1.The dust will get into the nooks and crannies of your models, which will be hard to remove,
2. The dust will get onto the plastic windows, which are very difficult to clean right to the edge, and regular cleaning will cause the plastic used in the windows to 'mist' and lose their transparency.
3. Physical damage can occur from the polishing duster catching on the small aerials/mirrors or other small parts of your model collection.
4. Spray polish, deodorant, hairspray and air fresheners will leave a film of muck on your models which can be difficult to remove, and can also react with the plastic or paint to cause cracking/crazing.
UV light will fade the paintwork on your models, it can also turn the plastic windows cloudy, yellow and/or brittle.
Physical damage can happen in many ways, children and visitors will pick them up, drop them, or knock them. The models can also be damaged during cleaning.
The answer of course is to put them into a display case, this will protect from all of the problems of the dust, and if you buy an acrylic display case, it will protect from at least 90% of the UV light. Some glass display cases may protect from a proportion of UV light, please check with the manufacturer before purchase, as glass has varying degrees of protection against UV light. A display case will also greatly protect from physical damage as it will deter visitors from admiring your model collection with their fingers.