I think hashing your sequence twice with different salt suffixes will make it much stronger, if not unbreakable for the next decade. Or am I missing something?

So, for input sequence t a better hash can be computed as

  md5(md5(t + salt1) + salt2)

Once computers get more powerful just add one more step with saltN, and so on.

Upd: length of t can be included in calculation as well.