Why should one tell the truth if it's is to one's advantage to tell a lie

This is the question lingering in Wittgenstein's mind, when the 20th century's greatest philosopher was only eight. He probably believed it has no harm to lie, quite a shock to many who rightly believed that Wittgenstein was a truthful person. Wittgenstein always had his own reason. For a layman such as myself, I think of this question, capably, only from the perspective of the advantageousness of telling a lie. The reason why I seldomly tell a lie is entirely due to the fact that I know I cannot gain any advantage by telling a lie with a long view. Wittgenstein is right that it is nothing wrong to tell a lie in such circumstances, that is to say, when it is to your advantage. The only part that is missing, deliberately or otherwise, is for how long. I may tell a lie and get away with a felony I did at a certain point in time; for which it is to my advantage to lie. However, if I have to lie continually thereafter and those lies become inconsistent among each others, which I say consciously or unconsciously and as a result of the utterance of such words and such inconsistency arising therefrom, I put myself in a situation far more difficult than when I did my felony. And more importantly, if I am frank about the felony from the outset, I am forgiven; then obviously telling a lie in this context is truly not to my advantage.

The question remains, how could I know whether, at a certain point in time, it is to my advantage to lie or to be honest? The answer is not straightforward and easy. But I think it is answerable, with certain disentangling of the world's fundamental values. What are the fundamental values? First of all, it is the complexity of the lie. If the lie you have to make up is complicated, the chance of its being spotted as a lie is higher. Secondly, the time frame you have to maintain the lie. The longer the time frame, the more likely you will slip some truth out of the lying process. Thirdly, the seriousness of the consequence if the lie is revealed. Normally this follows the fourth point. If level of seriousness is high, you may probably avoid lying from the outset. However, having said that, one may avoid the seriousness of the consequence if the truth is told and therefore lie, which is the fourth point I wish to make. We need to weigh on the two - whether the seriousness of the consequence if the lie is revealed is higher than that if the truth is told from the beginning.