Had a similar experience with a season ticket, ordered online. After a month it had faded to almost unreadability. The regular train crew knew who I was so continued to accept it but someone on the station said I had to get it replaced. Easier said than done.
The online retailer had to send instructions to the station ticket office to get them to set up a new record.... (for some reason the retailer was not using the same system as the TOCs) which they eventually agreed to do. Not sure why they were reluctant to do so, it wasn't going to cost them anything other than a few minutes time, whereas I was staring down the barrel of a loss of £1,200 for something that was not my fault.
New ticket has faded somewhat but hopefully will last till December. There does seem to be a lot of variability in the ink used - sometimes my ticket won't fade, other times it does (though it usually lasts the year out more or less).
Any ideas about the reluctance? Merseytravel also seem reluctant to replace lost seasons - they will only do it once. Why? They have a record of you paying money for the ticket which is linked via the photocard to you as an individual. OK, maybe they're punishing you for being careless but since this can set you back up to £1,000 it's a bit of a harsh punishment.