(65)At any time during the period of validity of the dynamic purchasing system, contracting authorities should be free to require economic operators to submit a renewed and updated self-declaration on the fulfilment of criteria for qualitative selection, within an adequate time limit. It should be recalled that the possibility foreseen in the general provisions on means of proof of this Directive to ask economic operators to submit supporting documents and the obligation to do so of the tenderer to which it has decided to award the contract also apply in the particular context of dynamic purchasing systems.