Soundness of mind

Is there a word lastingly?

Yes, the word ‘lastingly’ is an adverb that means ‘for a long time; in a lasting manner’. It is often used to describe something that is lasting or enduring. For example, «The effects of his generosity have been felt lastingly.»

What is a word for lasting a long time?

The word you are looking for is ‘enduring.’ Enduring means to last for a long time, to remain firm and unchanged despite opposition or hardship. For example, when describing a relationship, a person could say that it has been enduring for many years.