durably

rigidly securely solidly soundly strongly thoroughly tightly

hard

enduringly fast fixedly inflexibly like a rock motionlessly solid stably steadily stiffly substantially tight unflinchingly unshakeably

changeably flexibly indefinitely movably waveringly weakly

always endlessly eternally permanently

evermore perpetually

enduringly everything considered for always for ever and ever for good for keeps for life forevermore immortally in perpetuity in perpetuum infinitely interminably lastingly now and forever on and on till Doomsday till blue in the face till death do us part till the cows come home till the end of time unchangingly world without end

briefly never temporarily