Do you like the feel of the ball coming off the clubhead, the look of the irons at address? If so, then it may be a good idea to reshaft, if you think they've run their course for you, i.e. need a change of pace then maybe look at replacement irons either new or used.

If I like the feel and setup of an iron but something seems like it's missing -- either consistency or a weight problem -- then I wouldn't hesitate to try and reshaft, most of the times it's cheaper. What's the condition of the irons too? Consider the overall picture and your budget and you can then determine where to go with it.