Going nova during a wilderness trek is much more reasonable than when you're assaulting a dungeon, for instance.
In your games, sure. In my games the players always cautiously mete out their limited resources, even if they think they are probably only having one or two encounters before getting to recharge, because they know they might be wrong and something unexpected could happen that they don't want to be too low on resources to deal with.
Attunement is not a cost at low levels, because it is unlikely a character has accumulated more than three significant items that early.
That makes about as much sense as saying that the wand in question isn't overpowered because it is unlikely a character has acquired it at such a low level - since according to the magic item tables presented in the DMG there is a 0.03% chance the wand is rolled as part of a CR 0-4 treasure hoard, and a 0.04% chance it is rolled as part of a CR 5-10 treasure hoard.
Attunement is a cost, even at low levels, because with that attunement comes the fact that the party spellcaster much choose between using the wand as their action or using their action for something which might be more relevant to the situation at hand, and no one else can just grab the wand and use it because they don't have something better to do with their action either.
What makes it feel like it isn't a cost? That'd have to be something going on in your game specifically, and it is definitely something you can change if you want since attunement always feels like a cost in my campaigns.
As for the scroll suggestion, I sincerely hope you would be much more excited about finding this wand than a scroll of LB.
Finding the wand as it exists in the DMG, that'd be more exciting than finding a scroll. Finding your version? Not so much since it is 1 lightning bolt at minimum potential and with a save DC that might actually be lower than my own in just a few levels, and it might only be every few days that I can cast it, so for most cases I am better off using the scroll to add the spell to my spellbook, keeping it prepared, and casting it whenever it happens to be useful - leaving aside that seeing my DM being afraid that the game is going to "break" under very light stress would likely shake my confidence in the DM being able to provide the game I am looking to play.
What do you think of the item itself, Aaron? Am I too stingy?
I think you are clinging to a power level established by some prior version of D&D, or some other source besides the 5th edition books, and as a result are seeing things which are working perfectly fine and as intended (magic items are meant to feel like a bonus, and wands are meant to have enough of "oomph" to make spending their charges tempting enough that it actually happens, including that very last slightly risky one) as warning flags of "overpowered" or "broken" nature.
You are concerned about how many lightning bolts a 5th level party can fling at their enemies, and are completely missing that lightning bolt is not the answer to every problem, and when it is the answer there is nothing wrong with the party being able to provide said answer.
Should I transform it into a staff, perhaps allowing you to cast several lightning-themed spells (a level one spell for 1 charge; lightning bolt as 3 or 5* charges)?
Should you? Not unless you would actually be okay with the party having a staff that is even more potent than the wand you are already stressing over unnecessarily.
What you should do, in my opinion, is relax a bit and let 5th edition be 5th edition - and save the freaking and tweaking for
if your players express that they think it would be more fun to have their magic items be staggeringly less potent than those presented in the DMG (which are, in general, less potent than magic items of prior editions to start with).
