With the expression "it's been (length of time) since..." as in
1) It's been a long time since I've swung a golf club
2) It's been a long time since I've been to Augusta
...the present perfect implies that the action is something that is repeatable. The speaker has probably swung a golf club or been to Augusta more than once.
3) It's been a long time since I swung (not *swang) a golf club.
4) It's been a long time since I went to Augusta.
With a verb phrase that could be a repeatable action, the simple past (swung, went) could indicate a single event. The speaker in 3 may have swung a golf club more than once, but could also have done so only once. Similarly, with 4, "went to Augusta," the speaker could have gone there many times or only once. For example, one would say
It's been a long time since they cut down (not *have cut down) the old oak tree, but I still miss it
With verbs that denote a single, non-repeatable action, the present perfect is less natural. It would be odd to say
?It's been a long time since they've built their house
?It's been six years since I've moved to this apartment
?It's been two years since my dog has died
The present perfect is very often used with the time expression "since" if the verb has duration:
How many times has your fiance picked up the bill for dinner since you've known him?
She's never invited me over to her house since she's lived here
The simple past would not be appropriate, since it would imply that the knowing and the living are not still in effect.
Here are a few examples from Google of present perfect with repeatable actions:
It has now been 16 years since I've seen the places where I grew up in Michigan.
Its been several years since theyve spoken, and who knows what has happened in his life since?
It has been over two years since he's visited me at my house, and months since he's called.
It's been six years since he's had a drink, and about two years since he's smoked a cigarette. Those changes have had a direct effect on his health.
The present perfect is sometimes used in casual style with verbs denoting single, nonrepeatable events:
He said he's improved "leaps and bounds" during the three years since he's graduated from Kent State.
It's eight years since I've earned that degree.
No grammar sources that I know of mention this last use of the present perfect, and I would hesitate to consider it standard. The other uses, however--with verbs of duration and verbs denoting a repeatable action, are standard English.