Scanner images suddenly lack definition.

Epson Perfection 1670
I scan postage stamps and this little buddy has completed
around 80,000 at a rough guess.

Recently, moire marks have been appearing across the odd image,
I thought the de screen may have been turned off by little enquiring
fingers,
I have "re set" all defaults, now scanned images at 600dpi are all hazy
and lack definition.

Any suggestions of what may have happened? or is it just tired out
and needs replacing.

Whilst on the subject, would like to archive pre-war stamp magazines
they consist of approx 60, A4 pages, double if I take out the staples.
Black and white.
May I solicit some recommendations of a medium priced ADF duplex scanner
would $500 AUD cover it?

Thanks.