The difference with the 2 Princes are that they are not just young officers serving in HM Armed Forces, William in the RAF & Harry in the British Army, But also Royal Princes expected to carry our royal duties. This includes undertaking such charity work as this.
Once William starts Search & Rescue (SAR) training there will be little time for this sort of work whilst he commits himself to 6 years in the RAF & SAR work. The training takes at least 1 year plus 5 years commitment to fly after that.
Harry having trained as a FAC (Forward Air Controller) can expect to go aboard again in the next 18 months, then promotion to Captain and command of his own platoon & company.
They are still both young & enjoying their lives away from the media.