When hotdogs are going bad the hotdogs will usually turn to a more gray or brown color instead of the reddish color they are when good.
The bad hotdogs will also start to get slimy and have a terrible smell to them as in a really sour smell.
If the hotdogs are slimy and smell sour or have turned a different color then they're likely bad and should be thrown out.
Hotdogs will usually keep good in the refrigerator for up to 7 days but if you want to keep the hotdogs longer than 7 days then you should put them in the freezer.
When hotdogs are kept in the freezer the hotdogs should keep for up to 6 months to a year.