Why actually wait another 2 years? If you have the plot of land, you should start as soon as possible...
Whether "one" should start building as soon as possible after purchasing the plot of land, in my opinion, cannot be said so generally. What speaks against waiting? Especially if the plot is already available and was (presumably) paid for or gifted with equity. The plot doesn't go bad. Whether it lies unused for another 2 years or not does no harm. Of course, as long as there is no building obligation for the plot within a certain time. We also bought our plot of land in December 2014, so 2 years and 3 months before construction began. For us, that was exactly right; we already knew back then that we definitely wanted to build in a few years, but it was not yet the right time for several reasons. The plots in our desired building area were sold back at the end of 2014 and that was probably the last new development area for roughly 10 years (small town). So there was only the choice: buy now or later not be able to build in our desired location. So we bought. We had the equity for it. We then left the plot unused for 2 years. It didn’t harm it, nor us. On the contrary, the immediate neighbors had already started building before us during that time, so we could adapt accordingly, for example, so we wouldn’t build large floor-to-ceiling windows with a view of their garage, etc... I would do it the same way again. If building doesn’t work out after all, you can sell it again if necessary. In our case, the plot was very cheap (as I said, small town), so in case of doubt, we wouldn’t have "wasted" too much money (real estate transfer tax, notary fees, etc.). Plots usually retain their value well, so you can get out of the matter without major losses.