Daniel Wilches , your explanation is prefect ! thank you !

Without the interrogation sign at the end, it means "but", for example: Your grandma cooks very well. She doesn't like cooking, though. Is the same as: Your grandma cooks very well BUT she doesn't like cooking. With the interrogation sign at the end, it implies whoever says it is looking for a confirmation (as Adam says in his answer): Mom: Your grandma cooks very well. Son: She doesn't like cooking, though? This means, the son thinks the grandma doesn't like cooking, and is looking for a confirmation from his mother that indeed the grandma doesn't like cooking.

When added to a question in this form, it suggests that “it” has indeed been around for awhile.

Hi! The "though" suggests that the person asking the question already believes that the answer is "yes". The asking is looking for confirmation. It's a little like, "But it has been around for a while, right?"