I built a 4-plex in 1985 and had 4 lowboy's in the crawler. The 4 went bad within a few months of each other in 1997 and were replaced. I need to anticipate replacement again and I understand the lowboy's are no longer produced. Space is tight so I'm considering maybe an electric low profile or maybe a tankless?? I think what I have now are 30 gallon and I have not had any complaints about enough hot water. Any advice or thoughts would be appreciated.