How long do we keep pre operational expenses, then what do we do with these ?

I am not sure that we depreciate them but I think we need to capitalise them ? Then how do we write them off ?

This are expenses incurred prior to incorporation. Subject to management decisions, it could be written off in the first year of commencement of operations , or immortalized in the books, or capitalized and written off over a period of years reasonably determined by the management.