This week i started learning “Revelations” from Iron Maiden. It is a fairly simple song for me rythmwise (i did not checked the solo yet). If i pick a single riff i can nail it in some minute with no problem. But i feel i’am fairly slow in putting it all together and make the full song mine. I’m growing old (46) so i suspect that my ability to memorize is start failing.
How much time do you invest to learn the rythm part of a song?
Oh well… Anywhere in between 30 minutes to 3 years really…
Seriously though, it depends on the difficultynof the song in question. I’d like to believe that with the help of at least some basic tabulature I could make a passable version of a Maiden or Metallica song’s rhythm parts that I haven’t played before in a couple of hours. But if it’s some demanding stuff, like a song from my current favorite Revocation, well, that’s when I need the 3 years…
Well, if you know revelations i think we can agree that as far as riff goes is an easy song. I can spot a riff in 3-5 minute and ail the whole song in 30 minutes. But i’m more concerned in nail a full playthrough of an easy song without the support of a tableture or similar (i often use gpro or goplayalong to scroll the tab automatically) and only using memory. Just like you should learn it for a live show, i mean. Still fit in the 30 minutes time for you?
If you play along enough to something like guitar pro and don’t stress about it like if you make a mistake, just continue playing, you will get the song committed to memory in no time.
Yeah that’s a good question bro. I would have to say that would depend on the riff. I like to play some speed metal. It definitely pushes your boundaries…
I think it best to work on putting together several (or a few…) songs as if your going through your set list. Working on only just one song can get monotonous.
As you keep working on those songs, then eventually adding new songs you will start to notice thing getting easier.
Anyways I hope this helps
Best Regards,
Frisco
Just gotta practice and get away from the visual cues and focus and feel on just playing the song and singing (if you like to sing) the song…
Eventually things will get easier with time, practice and repetition.
Riff~Life 
I was thinking as long as it takes… If you have a problem with a part of the song try to come back to it later and move on to the other parts.
Eventually you can break it down and find your way around playing those difficult leads or riff’s, even if you use your own way to Express yourself.
Most times for me it’s hard to get the fingering patterns of someone else however you can certainly compromise.
Most times things moved so fast it’s hard to sound like someone else. I certainly had to compromise and work some parts with great success.
Most people don’t hear these little nuances although I focus on just getting it to sound right
Best of luck,
Frisco
Like I said: it really depends on how demanding the song is. But here’s a fun fact: I can’t seem to remember my own riffs for the life of me… 
If I don’t tab it out/videotape myself playing it right away, chances are that in a few days the riff will be gone forever…
If you get it down would love to see it.
Some songs I learn in a day and then spend about a week cleaning it up and playing along with the backing track to get my anticipation and timing right.
There are songs I have been working on for months and have months to go…it’s about your skill level and what feels natural to you. Some songs seem completely foreign to me, like I’ve never seen a guitar in my life. I have no comfort with the playing style. My hands and fingers get tied in knots. It’s in a completely different language! Those take a long time to learn. Other songs, my hands just seem to already know what to do. It’s maddening sometimes.
reminded me of my effort in learning the bohemian rhapsody guitar solo. it’s just a 40 sec solo, not so fast, still it took me weeks to get somewhere close… still far off though.