Up to now I've been quite lucky with my use of old, expired E-6 film.
I'm not into cross processing at all. This is a very personal opinion : I feel that good results are "happy accidents" mostly. I -may- try this one day but only with "available new" film.
I prefer to bath "unavailable new" positive film in E-6 chemistry.
So I had the opportunity to have a sizeable collection of old stocks for cheap and here's how it went :
- Fujichrome Sensia (exp 2003) : Nice colors and contrast, a bit dim (1/4 of a stop lower) some rolls have a tiiiiny bit of a green cast.
- Kodak Ektachrome E100VS (exp 2011) : In your face colours... And contrast : No color casts but my first roll was 1 stop under, rated the next ones at 50 ISO, looked brilliant then.
- Fujichrome Velvia 50 (exp 2004, old recipe) : Colors are wonderful -but- a tad of a green cast in shadow, beneficiates of +1/4 stop to give them a punch.
- Fujichrome Velvia 100 (exp 2005) : All over okay. No casts but dim sometimes. +1/4 on darker scenes.
To conclude : I'm glad I've been given that opportunity to test my skils at shooting and developing slide film using old stocks. That is an interesting challenge and made me better at using fresh slide film.
Example with Sensia :