correct?

I think there must be some reasons for lasting that much the life span of a market.

Is that sentence correct or not?

I am not a native English speaker! So better not to take from me! :-)

Are you talking about a particular market or just markets in general regardless of time? So maybe it depends on what your case study is. Here are some suggestions:

I think there must be reasons for a market to last such a long life span.

I think there must be reasons why markets have such a long-lasting life span.