I collect lots of Pokemon merchandise, not sure exactly why, anything Pokemon related and given that I have enough money with me at the time I'll buy it. Doesn't matter if its plush toys, plastic figurines, clothing (that actually fits me - adult size XL), TCG boosters, boxes, or tins, movies, or games. I have to have it. Most of my collection is posted in RNC topic (link on the first post above), anything new I get (not TCG related) I try to post a photo there.
Plush toys are main source of buying Pokemon merchandise, brings me comfort and in a way, at nights, keep the nightmares away (not monsters, demons, or ghosts, when I get those I think of it as being "in a music video" thanks to me liking metal music - but my main phobias, mainly dying in some sort of natural disaster separated from family, or me not being able to save them). Yes, I sleep with a plush Pokemon every night (I change often). I don't get nightmares of any kind, unless the plush falls on the floor during the night.
It also keeps me from buying lots of sugary treats or drinks (its what I would spend most of my money on before) - which isn't good for my diabetes.... but before I buy Pokemon merchandise, I have to make sure I set money aside for medication and bills. At the store, now I'm like "Chocolate or Pokemon? - I'll go with Pokemon, chocolate some other time"
Although I think I answered most of the questions, I'll still answer them:
• Do you collect pokémon merchandise? - Yes, a lot. Anywhere I find it (and if I have enough money at that time) I'll buy it, doesn't matter if its a Pokemon I like or not
•Why do you like to do that? - I would say, it brings me joy - prevents me from purchasing sugary treats
Alternatively: why don't you do that? - doesn't apply to me
• Do you feel there is enough or too much pokémon merchandise available for you? (Where you live or on the web or anywhere). - In Seattle (or the surrounding cities - Everett, Bellevue, & Tacoma) there isn't much on the figurines, or the plush toys (those I have to buy online). Most of the Trading Card Game stuff I can find in most of the big stores (like Target & Toys R Us), same for the Video Games.
• Is there some kind of merchandise you wish existed but haven't seen yet? - Most of the plush toys I want to try and find I never seen available anywhere. For some (like Persian or Furret or Zangoose or Floatzel - my favorite Pokemon from the older generations) I don't think any where made, so in a way there isn't enough of them.