Deadlines for offers should be extremely short. Ideally they are under 36 hours. There is even a good argument for deadlines to be under 20 minutes (as long as the employee knows it is coming).
Beside the obvious criteria for a great employee (smart, gets things done, etc), the number one (less obvious) criteria is that they REALLY want to work at your company. They will be so much more effective if they really want to work for you.
They need to have a REAL attraction to your company. Maybe is is because of the company’s mission. Maybe is is because of the culture. Maybe it is because of the people (or their direct supervisor). Maybe it is because of the technology. Maybe it is to get rich. … there could be MANY reasons … but that reason has to equal a genuine excitement to join your company that is beyond the rational pros and cons.
This is why you should give offers with a really short deadline. If someone needs a lot of time to make a decision whether to join your company or not, they probably are not super excited about your company. They still could pick your company and be a solid contributor … but my experience is that they rarely turn out to be amazing.
The a phrase in romance “he’s just not into you” applies in recruiting as well. You want people that want you. If a candidate, after the hours and hours of interviews, projects, reference checks, etc. still needs more time to decide to join your company or not, you should move on.
Summation: to most optimize for a 10Xer, keep deadlines for offers short.