how long before mochi turn bad?

I will leave Japan soon, a friend asked me to bring her some mochi but she can get them from me in three to four weeks.
If I buy them now, will they be ok for that time?

Haf,

The dried/hard stuff that you buy from supermarkets lasts for years provided it is unopened.

Thank you Dave, I will look out for them.
Yesterday I was at a few sweet shops and the fresh ones that they sold only lasted for max. 3 days.

The dried hard version doesn't have any bean filling, and needs boiling or toasting to be edible. If you like the beans you can buy them separately (sometimes in cans, sometimes in plastic packs) and heat the paste together with the mochi to make zenzai.

Haf, Dave is correct but let someone check the "shomi-kigen" date on the package to be on the safe side. They would be easy to carry on your flight home as well.

But at the same time, if you freeze mochi in your home freezer, it can almost last forever. If you prefer to buy fresh mochi from your local mochi shop, freeze 'em!

Thank you all very much for your answers! I now got different kinds of mochi, fresh ones, omiyage packaged ones and dry ones. I will just put them all in the refrigerator and the fresh ones in the freezer and hope for the best. ;)
Well, I just arrived back in Germany *sniff*, but I hope I can get back to Japan as soon as possible after I'm finished with my studies. Hopefully a computer company or so will take me in. Or I'll work in a foreign butler cafe. (just kidding ^^)

Haf, any kind of mochi should NOT be put in the refridgerator, because it will become hard and difficult to soften properly. Leave it in room temprature (a wine cellar might be ideal) if the label says it's okay, or otherwise freeze them.

So what can you do if they already have become hard due to refridgerating? If they are sweats in which you don't want to ruin their shape, try steaming when you want to eat them. If they are ordinary plain mochi, stew them but make sure you don't stew them too long since they will melt.

Oh, thank you Uco, I'll take em out immediately. I wrapped them in a bag before putting them in the refridgerator, so I hope they are still soft.

Mochi is tricky for the extreme elderly, because (A) a lot of them don't have healthy teeth to bite them in pieces and (B) their throats tend to dry therefore making it more difficult for mochi to be swallowed down.

So when feeding elderlies, you are encouraged to cut mochi in tiny pieces so that even if they fail to chew them enough before swallowing, it will still leave a space to breath inside their throats. If they happen to swallow a big lump, vacume cleaners are a handy tool to pull it out.

I've never heard about taking extra care when feeding mochi to toddlers, but I suppose that (A) toddlers' throats are not as dry and (B) you take extra care anyway.

I think the tricky part about mochi is that the Japanese tend to expect elderlies to be used to mochi, while in reality they age and are not who they were yesterday. Meanwhile, you expect toddlers to be weak, so you cut everything in pieces and keep a good eye on them anyway.

One thing we are encouraged to keep in mind however are to avoid feeding "kon-nyaku jelly" to toddlers. Kon-nyaku jelly are tiny cup-shaped snacks that were invented in the recent decades. But unlike gelatine jelly, it doesn't melt in your mouth. It contains more fibers and therefore will not break up unless you chew them (which is the reason it's good for people trying to loose weight).

People tend to miss out on this fact, expecting it to be similar to gelatine jelly (which is also available in similar shapes), hence the warning. Also, these tiny snacks can be very attractive for toddlers when left in the cupboard.

I suppose it's all down to the balance of what you expect and what reality offers you.

Oh my god, it seems like I posted a response to a new message just as it was assumingly removed elsewhere by the webmaster.