When I was a young kid, like 5 or 6 years old, I was given part of a stamp collection that had been from my father , in his youth. He stopped quite soon, lost interest. The other part was given to my brother.
IIn that time I actively colected stamps, getting them off envelopes, trading them with friends, who got them from envelopes, etc. Every now and then (birthday, santa claus) getting packages of stamps. All in all, it didn't cost me, as the stamps all came from envelopes. I also got the colection of a sister of my grandfathers, when she died. I didn't know the woman at all, but the stuff had to be divided amongst the survivors and my grandparents thought it would be neat for me (my brother had already stopped). I was like 8 or 9 at the time.
Then, I also started picking cents out of change, to build up a year set, and when that was nearly complete, I started with 5 cents "stuivers" as well. Didn't have much money to spend so started with the small denominations..
At some point, when collection coins became more expensive (I had 1 cent, 5 cent and 10 cent nearly complete and taking 25 cents out of change had a larger impact on my cash flow), the coin collection went into hybernation.
The stamp collection did that a few years afterwards, for a similar reason as AEtheling said: the commems. It became impossible to keep up with the PTT to collect all those commems they're issuing: hey the sun shines, let's issue a commem to that.
For many years I didn't do much with both collections, other than picking a stamp from an envelope, when it looked neat, or when I found a coin that could fill a hole in my collection.
I still have the albums (and cigar cases) with stamps, but I hardly look at them anymore.
Coin collection woke up when I started traveling and I took home coins from that country as a souvenir. Then I finished my study and started working so had a lot more money to spend on the coins and I started filling holes in the 25cent, 1 gulden, 2.5 gulden, 5 gulden, 10 gulden and 50 gulden coins.
Introduction of the euro also did a lot. Gulden coins becoming much harder to get, made me look for different sources and I discovered Ebay and a dutch auction site.
I fould a coin there that intrested me, but I wanted more info on the coin, so I looked it up on internet. One of the highest ranked hits was OmniCoin.
There I found a neat picture of the coin I was looking for (i have no idea which coin it was) and also a link to "discussion forum", which brought me here.