Raspberries are naturally renewed every year if you cut back the old canes that bore fruit each fall to allow the new growth (green shoots) to take over in the spring. The patch can stay in the same place for years but you will need to thin out the canes so they have better air circulation. The best time to remove the canes or thin them and the best time to remove the canes and start a fresh patch is early spring just before they leaf out or in the fall.  To increase yields you can dress the roots with well rotted manure in the fall, add Osmocote Plus to the roots in the spring and make sure you weed around the plants so they don't compete with weeds for water and nutrition.  When thinning the canes or planting a new bed give them 8 to 12 inches of space between plants. Hope this helps to keep you in lots of jam. Keep growing, Marianne Binetti