Railcards applied for online and sent out by post are issued on plastic cards, aren't they, and presumably don't fade?
Doubt putting one of them near a heat source would be a good idea, anyway.
Dis cards have been plastic atleast 10 years. I accidentally melted one in tumble dryer after washing it along with my passport, which totally melted the front of the railcard and bent it. Date was unreadable. The passport fared slightly better but was still unusable.
I'd proper screwed myself as I was travelling up to Crewe from Folkestone that same day to house sit for my sister and already had my tickets.
Tried explaining it at Folkestone Central ticket office, but obviously they couldn't do anything as they have no control or authority to issue DPRCs. Was advised to show the semi melted artifact at Euston and see if they allowed me to travel, which they did no problem, and kindly informed the train manager too so I wasn't troubled.
Though an expensive mistake for me passport wise, I did actually get my hands on a replacement passport collected from South Africa House in Trafalgar Square two days later on way home. Two days before my replacement railcard landed on the doormat.