A couple of factors have to be considered for storing fruit long term. One is temperature. Two is ripeness. The riper the lemon when picked, the shorter the period of storage. For lemons, the best method may be to seal unused lemons in Ziploc bags and keep them in the crisper drawer for up to one month. Storage past one month would require them to be picked green and kept at temperatures around 10-12 degrees Celsius (commercial cold storage) with humidity control. A better option may be to freeze the lemon juice or rind for later use and discard the rest. Whole citrus fruits should not be frozen.