The Multigrade III and the Polycontrast are prehistoric, so don't bother with those. For the others you could send the batch codes to Ilford with a nice note asking for the approximate production dates -- if they are more than five years old then you will likely lose some maximum contrast and/or gain some fogging. Personally, I'd suggest not purchasing unless you have a use for old paper (the fibre-based materials could be fixed out and used for some alternative processes, for example).