I have 3 which I have recently renewed, but the renewal price: $75 for the first, followed by $60 for the subsequent names (same as original registration costs without the $5 coupon code from jp-domains.com), caused me to seriously review whether to renew or not each of them one by one, so I would recommend you do the same. I doubt if one should normally have say more than 5 .jp names in an individual portfolio eg, looking at your signature I would keep cheaphotels.jp, drop musicdownloads.jp and wobble over onlinedating.jp.