Is the investment in bonds permissible for each FYs

Sec. 54EC grants deduction from taxable capital gains on transfer of a capital asset to the extent of investments in notified bonds within six months from the date of transfer of such asset.

Therefore, You will be get a exemption only in the capital gain and thats also only in the year of arising of capital gain.
So, if you want a exemption u/s 54EC of income tax act,1962 whenever capital gain is arising in sale of capital assets you need to invest in investments in notified Bonds