import functools
import time
from collections import OrderedDict

class LRUCache:
    def __init__(self, max_size, expiry_hours):
        self.cache = OrderedDict()
        self.max_size = max_size
        self.expiry_seconds = expiry_hours * 3600

    def __setitem__(self, key, value):
        now = time.time()
        self.cache[key] = (value, now + self.expiry_seconds)
        while len(self.cache) > self.max_size:
            self.cache.popitem(last=False)

    def __getitem__(self, key):
        value, expiry_time = self.cache[key]
        now = time.time()
        if now > expiry_time:
            del self.cache[key]
            raise KeyError
        return value

    def get(self, key, default=None):
        try:
            return self[key]
        except KeyError:
            return default


def lru_cache(max_size=128, expiry_hours=1):
    cache = LRUCache(max_size, expiry_hours)

    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            key = (args, frozenset(kwargs.items()))
            if key in cache.cache:
                return cache[key]
            result = func(*args, **kwargs)
            cache[key] = result
            return result

        return wrapper

    return decorator

# Example:
@lru_cache(max_size=100, expiry_hours=8)
def slow_hello_world():
    response = time.sleep(10)
    return "Hello world!"