Is it ok if they left my nasogastric tube unchanged for more than two weeks?

Depends, usually yes: Most ng tubes are designed to be left in place as long as they are needed for drainage and/or feeding after serious injury/illness or when recovering from major surgeries on the digestive tract. Replacing an ng tube, especially after certain types of surgery, may actually risk causing new injury. If we expect to need a tube for more than 4-6 weeks, a more permanent tube may be placed surgically.