It's well known that it's impossible to time the market and therefore short term investment is usually not a good idea for occasional investor. At the same time, long term investment is almost always profitable. Now, where is that boundary between short and long term? I do understand that it's not as clearcut, but some guidance would be useful.
In my specific case, out of my savings, there's about £25-30K chunk that I don't immediately need, yet it's sitting in a savings account earning a near-zero interest. I will need this money in about 3-4 years time - and I can't afford to "loose it all", although I can risk a small hit (up to 5%) - of course, I want to maximise the return. I also have little flexibility about stretching this time period (maybe to 5 years, but not more). I'm trying to come up with the best strategy to make this money work.
Note, this money is not my "emergency fund" (that one is different and sufficiently funded).