I have used Palo Santo sticks until they are gone. You can relight them as many times as you need to or want to… when they get smaller or too small, I have lit them & placed them on a screen top on my cauldron or broken them into even smaller pieces or slivers & used them on charcoal discs. I sometimes take the smaller pieces or slivers & use an electric coffee grinder to zip them a couple of times to use either in fresh incense or on the charcoal discs. 
Others may have some other ideas for you too. You could also if they get to be unable to hold & none of the above is something you would do in your practice, if you have a fire 
& when it gets to like smoldering put the smaller piece or chunk on the smoldering coals.