In order to avoid sleeping for long periods of time, switch to a frequent polling mechanism, so the success case is fast.

example_usage.rb

expect{current_path}.to eventually_eql('/')
expect{current_path}.to eventually_match(%r{/boxes/PS\d+/shipping_information/new})
expect{get_me_the_cookie('foo')[:value]}.to eventually_eql('bar')

polling_matchers.rb

require "timeout"

module PollingMatchers
  extend RSpec::Matchers::DSL

  def eventually(actual_block, operator, expected)
    Timeout.timeout(Capybara.default_wait_time) do
      sleep(0.1) until actual_block.call.send(operator, expected)
      true
    end
  rescue TimeoutError
    false
  end

  matcher :eventually_eql do |expected|
    match do |block|
      eventually(block, :==, expected)
    end
  end

  matcher :eventually_match do |expected_regex|
    match do |block|
      eventually(block, :=~, expected_regex)
    end
  end
end