If somebody has nodular melanomas or 6 or so years, will it visibly continue to grow in size?

Yes: Melanoma is a fairly aggressive malignancy with a significant history of metastasis a much more problematic issue than local growth. No one should have a melanoma left untreated for a 6 year time frame. I question wether you are referring to nodular basal cell carcinoma which also needs to be excised but does not have the metastatic potential.