I drive mine weekly sometimes I miss a week. When I replaced the battery my mechanic told me unless I'm driving it daily to hook it up. When you allow a battery to discharge it can never return to the original level and through time it will eventually shorten the life.
My original battery lasted only 3 years, had I used the battery tender It could have lasted 5 or 6.
In lambo's you don't need them like other exotics. At least for the Gallardo, it really isn't needed, but I guess if it sits for more than 2 weeks I'd say yes, but these cars do great with batteries if not sitting for more than 2 weeks.
My cousin has one for his Gallardo but hardly remembers to put it on. Clients Huracan definitely needs his battery tender on all the time. I have always had one on my Diablo. It was something I was told to do first up so I continued. I did go away for a book launch for 3 weeks and forgot to put the battery tender on. When I returned, the Diablo fired up but not as easily as it normally would have when the tender was connected.