Uganda Visa Validity:

If your departure for Uganda is more than 1-year from now, you must wait to apply. Please submit your request when you're within 1-year of your planned departure.

The Uganda visa is typically issued for a single-entry, valid for 90-days from the date you will enter Uganda as stated on your visa application. 
Multiple-entry visas with a longer validity are also available for business and tourist visas but require additional documents: police clearance, 2 letter of recommendations from Uganda and proof of entries and exits.