Now that they explode on breaking, that sounds like a good way to get an unarmoured limb or a head burnt off.
Edit: OK, I went into wizmode and actually tested this. Aside: are item frequencies different in wizmode? I found an unbroken helmet of understanding on UT1!
As for wielded items breaking, I tried one gas grenade and two lanterns, with no other equipment of any kind. The gas grenade broke after a fighting just a few monsters with it. The lanterns were much more sturdy. I died about 10 times more often than than a wielded lantern broke. The two monsters which succeeded in breaking the lanterns were a greater carnivorous plant and a kobold with a mace, when I blocked an attack. The kobold's attack killed me (because of the mace damage, not the lantern's explosion). I forget whether the carnivorous plant's attack killed me. In any case, both explosions set my scrolls of wishing alight. I didn't carry any wands, so I don't know if the explosion was powerful enough to break them.
In conclusion, lanterns are terrible weapons, but they're less likely to kill you than hedgehogs.
SPOILER ALERT. Click here to see text.Broken lanterns are viable weapons to kill Genetrix Vesana with, but she might kill you a few dozen times first