Downs (and ups) of record values

I received the Rare Record Price Guide 2014 today (yes, 2014 - they like to be well ahead of the game) and I have to say it has been a rather deflating experience. It seems that the values of many of the records that I own, or would like to own, have come down steeply over the last two years since the last guide was published. I'm talking in particular about 1950s and early 60s rock and roll and pop records, the values of many of which have declined by 25 per cent. Rocket by Joe Bennett and the Sparkletones has apparently reduced in value from £200 to £150, while Mr Lee by the Bobbettes has come down from £80 to £60. Other lower value records have disappeared from the guide altogether. It's inevitable, I suppose, as collectors of my generation gradually lose interest or die, with their collections flooding the market.
There are bright spots, of course. Sixties soul records have held their value while some ska and Northern soul records have increased in value. But the biggest rises have come in the field of progressive and psychedelic rock and sixties freakbeat. Zoot Suit by the High Numbers on Fontana, for example, has gone up in value from £600 to £900 and the LP by Locomotive on Parlophone that I picked up last year has apparently increased in value from £375 to £900. Of course, as the guide freely admits, any record is only worth what someone is prepared to pay for it on any particular day. But it does seem that time is running out for rock and roll collectors and that the future can only mean lower returns when and if they decide to sell their precious vinyl.