Actually I only slightly disagree with your comment. What should we do? Well sitting around predicting is useless as the Lord will return at the appointed time and it will be the perfect time that man has nothing to do with, however that in mind knowing that the Lord can return at anytime what we are to do is the following.
Be patient therefore, brethren, unto the coming of the Lord. Behold, the husbandman waiteth for the precious fruit of the earth, and hath long patience for it, until he receive the early and latter rain. Be ye also patient; stablish your hearts: for the coming of the Lord draweth nigh. Grudge not one against another, brethren, lest ye be condemned: behold, the judge standeth before the door. (James 5:7-9 KJV)
But the end of all things is at hand: But the end of all things is at hand: be ye therefore sober, and watch unto prayer. And above all things have fervent charity among yourselves: for charity shall cover the multitude of sins. Use hospitality one to another without grudging. As every man hath received the gift, even so minister the same one to another, as good stewards of the manifold grace of God. If any man speak, let him speak as the oracles of God; if any man minister, let him do it as of the ability which God giveth: that God in all things may be glorified through Jesus Christ, to whom be praise and dominion for ever and ever. Amen.
But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up. Seeing then that all these things shall be dissolved, what manner of persons ought ye to be in all holy conversation and godliness, (2 Peter 3:10-11 KJV)
Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness. But grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ. To him be glory both now and for ever. Amen. (2 Peter 3:17-18 KJV)
For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord. Wherefore comfort one another with these words. (1 Thessalonians 4:16-18 KJV)
So we actually as believers have much to do as we look with anticipation to the Day when the Lord will return and not just staring at the clouds wondering when and why? Preach, teach, encourage, live a life that is holy and godly, love one another and be patient to mention just a few.