to use LN is atleast 1 deposit to vault funds up on the bitcoin network before even getting to play with LN and atleast one to unvault funds when finished playing around on LN(vaulting up with a factory to let the factory then handle the channel open/close management)
if you only plan on budgeting your money for 2 payments then its not worth it.

if you plan to avoid factories. you will end up needing to spread funds over multiple channels manually yourself. this can end up being more than 2 transactions onchain (atleast one(with multiple outputs) to vault up.. or.. multiple transactions of single outputs if opening channels at different times) and then multiple transactions to unvault the funds.

they say average users end up needing atleast 5 channels that have their funds spread out to atleast have a relatively good chance to spend some of the funds when needed) so thats like a minimum of 6 transactions onchain.

so if you are only budgeting to use LN for 6 payments.. its not worth it.

VISAUSA statistics have people that only use visa cards ~42 times a month (~1.5 tx a day) but bitcoin is not as widly available as visa. so people wont be spending as often. so lets say only 2 times a week.
so unless your planning ahead your spending habits for the next 3 weeks. again not worth it

LN's niche are for the spammers (day traders, mixers and those who do make regular payments to certain recipients)
it wont really have good utility for those that only want to buy groceries once a week or pay a monthly bill.. (unless they plan to vault up enough funds for 2-6months..

but as my previous posts suggest unless bitcoins network expands the transactions per day restrictions. expect to have to preplan funding a LN deposit for upto a years worth, once things get busier (which not many would want to do)

..
as for saying its instant..
thats if:
1. everyone on the route is online to agree
2. everyone on the route is funded enough
3. others havnt raided your channel of said route before you got to spend it yourself