nostalgic smells

i get really attached to certain smells from the past (usually grandparents' homes but sometimes other places from childhood as well) and i unexpectedly smelled my grandpa's house as i was walking into my room today. came back a bit later and it was gone, which made me realize: 

what if that was the last time i smelled that??

i won't be at his house ever again so really what are the chances that this will happen again... it's so comforting but sad at the same time because i know i can't go back