I don't think the data is correct. For what it's worth, we weren't allowed to use the data from flight tracking sites such as Flight Aware, etc in goverment legal cases involving illegal aircraft operation or in litigation resulting from an air crash as there are often errors in the data (the sites themselves having a disclaimer if you look).
I don't know what type of helicopters were in the air, but a common helicopter, the Bell Jet Ranger has a range of about 3 1/2 hours at cruise speed. An Apache helicopter - the pilots would plan about 3 hours. SAR helicopters such as the Bell 412, Eurocopter EC135 and Sikorsky S-76 have 3-4 hours of flight time. That time can be affected by factors like weather conditions, the need for additional fuel reserves, and specialized mission requirements. Some helicopters may be equipped with aerial refueling capabilities, which can extend their operational time significantly, but it's not common in civilian or non-military use.
Slowing down to search water or land will increase that, but you also have to factor in you are a lower altitude where fuel consumption is higher. On average, when we'd be looking at where a civilian helicopter may have gone down, range wise, if transponder (radar contact) was lost, we'd factor in about 4 hours aloft, maybe 5.
There are some very specialized military helicopters with a range up to 1200 miles. Advanced prototypes like the The Bell V-280 Valor, a VTOL (Vertical Take-Off and Landing) aircraft under development, boasts a range of over 2400 miles, but you're not going to see such types of helicopters in civilian search operations.
