Edit: I should mention that this is for a longtherm hold, about 5-10 years
first of all don't go all in. and even if you want to go all in, don't do it all in cryptocurrencies. try to diversify into other things. for example gold or stocks or anything that you find good as an investment, it may depend on the country you live in.
and since you want to hold these cryptos long term then I suggest only considering bitcoin for that matter, the other altcoins are not very good and both of these you mentioned are already in a big bubble (eth more than ltc).
although if you want my suggestion, I prefer investing in bitcoin only for long term and then picking up trading altcoins as mostly a short term investment, to buy in the dips and sell when they rise to earn even more bitcoin.