The tide comes in and out with everything in one way or another
Comic books, baseball cards, electric model trains, muscle cars you name it it's been bought n sold over and over again.
The players that play the game well have an uncanny sense to get out before a crash - then jump back in 'HEAVY' when prices are super low.
If you develop a rule sheet or a criteria that you will stick to almost religiously yet can tweak as time goes on then I see no problem buying a selling for the next 20 years.
- Of course what screws everyone up is greed and lust