Along time depends how much you go on a day. You can bot 24/7, which is what I did and i got it really fast. If you play legit 2-3 hrs a day then maybe like 5 months. If you bot 2-3 hrs a day it will be faster.
^Don't bot. Getting 60 to 99 Attack will take at least 150 hours, but as new monsters are being released, this is subject to change.
You are 18 levels away from level 99, and each level takes 10% longer than the previous one (the amount of experience doubles every 7 levels). That means that, although 81 looks like a high level, you are still missing about 4.5 times the experience you already have (and will take about 4.5 the time it already took you).
I couldn't find much details in the online guides (for example, runescape.wikia, or tip.it), on how much experience you get per hour. Perhaps you can check this, and help complete these guides. For example, use an attack that only gives you strength experience, and see how much experience you get in half an hour, or in an hour. Or use one that gives you shared experience, and add the experience you get in attack + strength + defense. (In any case, you also get constitution experience.)
Update: Consulting with some friends, it would seem that you can get 50,000-100,000 experience an hour, depending on your level, weapon, and other factors. You can base your calculations on that. In any case, you can reach level 60 fairly quickly.
Depends on how long you are on for, it can be 1-2 weeks if play constantly, or 1 to 2 months if played less constantly
It depends how long you are on Runescape.
depends on you're experience rate per hour e.g [45k per hour] and how many hours you train a day.
Not that long, it's almost instant.
Go to:runescpae
about 30sec or 1min
probibly 1-2 months because of the exp, but dont give up
well if you played runescape 24/7 it would take probealy take 2-3 days to do .
If you just started RuneScape maybe 30 minutes and if you already have a RuneScape account 7 minutes minimum.
depends on what your cooking
It just depends on your behavior.
as long as you want baby, i can go forever