[Broorbbub]

Well, "go to practice more often" is the simple advice to give. Let's choose to assume that you have serious reasons for missing practice for long periods of time. Maybe your doujou closes for summer vacations, for instance.

Anyway, once you've let yourself get out of shape, there's little you can do. Thus, if you have to miss practice, you should keep yourself in shape--and the way to do that is suburi. Suburi every day, maybe more than once a day. If you have 5 half-years' worth of experience, then you know what "correct suburi" feels like, so do it. Find a way to do suburi in your house--squatting suburi take little place and don't put your ceiling in danger. Make hayai-suburi a routine and you'll maintain your physical condition for as long as it takes. To ensure your form is not off, you could take a video of yourself and review it for mistakes.

Of course, suburi don't teach you distance and timing, so if you're lucky enough to have someone else to practice with, do kirikaeshi, kihon-kata, or even regular kata. If you can't find anyone... well, you'll still have troubles when you start again, but you'll be fine after 1-2 practices.

I hope this helps you somewhat.